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Ke, H.

Publications and source records attributed to Ke, H..

At least 37 records · Page 2Linked to original sources

Genetic disruption of isocitrate dehydrogenase arrests the full development of sexual stage parasites in Plasmodium falciparum

The malaria parasites encode all eight mitochondrial enzymes that can constitute the classical tricarboxylic acid (TCA) cycle. We previously reported that genetic ablation of six out of eight TCA enzymes had no significant impact on the parasite survival and growth in asexual blood stage; aconitase knockout ({Delta}ACO) parasites were, however, arrested as late-stage gametocytes. Herein, we describe a defective gametocyte development phenotype resulting from the knockout of another TCA enzyme, isocitrate dehydrogenase (IDH). Similar to the{Delta} ACO gametocytes,{Delta} IDH gametocytes stall at stage III/IV and cannot form mature gametocytes or undergo exflagellation. Both ACO and IDH KO gametocytes exhibit fragmented mitochondrial morphology. Knockout of IDH also exerts a fitness cost, leading to a decrease in growth rate in erythrocytic stages. We examined two possible causes for the phenotype in the{Delta} IDH gametocytes: 1. Accumulation of reactive oxygen species (ROS) within the parasite mitochondrion due to diminished production of mitochondrial NADPH during the 10-14 days of gametocyte development; or 2. Cytotoxicity of built-up citrate upstream of IDH. We found that antioxidant agents such as N-acetylcysteine and MitoQ did not rescue the phenotype of{Delta} ACO or{Delta} IDH gametocytes. Large amounts of citrate in the medium also had no significant effect on the gametocyte development or gamete formation of wildtype parasites. Our results demonstrate the importance of IDH in gametocytogenesis, providing evidence that IDH as well as aconitase could be further explored as targets for gametocidal agents and malaria transmission blockers.

microbiology↗

Antibody repertoire gene usage is explained by common genetic variants in the immunoglobulin heavy chain locus

Variation in the antibody response has been linked to differential outcomes in disease, and suboptimal vaccine and therapeutic responsiveness, the determinants of which have not been fully elucidated. Countering models that presume antibodies are generated largely by stochastic processes, we demonstrate that polymorphisms within the immunoglobulin heavy chain locus (IGH) significantly impact the naive and antigen-experienced antibody repertoire, indicating that genetics predisposes individuals to mount qualitatively and quantitatively different antibody responses. We pair recently developed long-read genomic sequencing methods with antibody repertoire profiling to comprehensively resolve IGH genetic variation, including novel structural variants, single nucleotide variants, and genes and alleles. We show that IGH germline variants determine the presence and frequency of antibody genes in the expressed repertoire, including those enriched in functional elements linked to V(D)J recombination, and overlapping disease-associated variants. These results illuminate the power of leveraging IGH genetics to better understand the regulation, function and dynamics of the antibody response in disease.

genomics↗

High-dimension to high-dimension screening for detecting genome-wide epigenetic regulators of gene expression

MotivationThe advancement of high-throughput technology characterizes a wide range of epigenetic modifications across the genome involved in disease pathogenesis via regulating gene expression. The high-dimensionality of both epigenetic and gene expression data make it challenging to identify the important epigenetic regulators of genes. Conducting univariate test for each epigenetic-gene pair is subject to serious multiple comparison burden, and direct application of regularization methods to select epigenetic-gene pairs is computationally infeasible. Applying fast screening to reduce dimension first before regularization is more efficient and stable than applying regularization methods alone. ResultsWe propose a novel screening method based on robust partial correlation to detect epigenetic regulators of gene expression over the whole genome, a problem that includes both high-dimensional predictors and high-dimensional responses. Compared to existing screening methods, our method is conceptually innovative that it reduces the dimension of both predictor and response, and screens at both node (epigenetic features or genes) and edge (epigenetic-gene pairs) levels. We develop data-driven procedures to determine the conditional sets and the optimal screening threshold, and implement a fast iterative algorithm. Simulations and two applications to long non-coding RNA and DNA methylation regulation in Kidney cancer and Glioblastoma Multiforme illustrate the validity and advantage of our method. AvailabilityThe R package, related source codes and real data sets used in this paper are provided at https://github.com/kehongjie/rPCor.

bioinformatics↗

Transcriptional changes in Plasmodium falciparum upon conditional knock down of mitochondrial ribosomal proteins RSM22 and L23

The mitochondrion of malaria parasites is an attractive antimalarial drug target, which require mitoribosomes to translate genes encoded in the mitochondrial (mt) DNA. Plasmodium mitoribosomes are composed of highly fragmented ribosomal RNA (rRNA) encoded in the mtDNA. All mitoribosomal proteins (MRPs) and other assembly factors are encoded in the nuclear genome. Here, we have studied one small subunit (SSU) MRP, RSM22 (Pf3D7_1027200) and one large subunit (LSU) MRP, L23 (Pf3D7_1239100) in Plasmodium falciparum. We show that both proteins localize to the mitochondrion and are essential for parasite survival. However, the parasites survive conditional knock down (KD) of PfRSM22 for two days longer than PfMRPL23 KD. RNA sequencing revealed transcriptomic changes of the nuclear and mitochondrial genomes upon KD of these MRPs. In the early phase following KD, while most mt rRNAs and transcripts of putative MRPs were downregulated in the absence of PfRSM22, several mt rRNAs and MRPs were upregulated after KD of PfMRPL23. At the late time points of KD, loss of PfRSM22 and PfMRPL23 caused defects in many essential metabolic pathways, leading to parasite death. There was a significant overlap among the mitochondrial related transcripts downregulated in the late phase of PfRSM22 and PfMRPL23 KDs. We have also identified a list of mitochondrial proteins of unknown function that are likely Plasmodium MRPs based on their structural similarity to known MRPs as well as their expression profiles in KD parasites.

microbiology↗

ORA47 is a transcriptional regulator of a general stress response hub

Transcriptional regulators of general stress response (GSR) reprogram expression of selected genes to transduce informational signals into cellular events, ultimately manifested in plants ability to cope with environmental challenges. Identification of the core GSR regulatory proteins will uncover the principal modules and their mode of action in the establishment of adaptive responses. To define the GSR regulatory components, we employed a yeast-one-hybrid assay to identify the protein(s) that binds to the previously established functional GSR motif, coined Rapid Stress Response Element (RSRE). This led to the isolation of ORA47 (octadecanoid-responsive AP2/ERF-domain transcription factor 47), a Methyl jasmonate (MeJA) inducible protein. Subsequently, the ORA47 transcriptional activity was confirmed using RSRE-driven Luciferase (LUC) activity assay performed in the ORA47 loss- and gain-of-function lines introgressed into the 4xRSRE::Luc background. In addition, the prime contribution of CALMODULIN-BINDING TRANSCRIPTIONAL ACTIVATOR3 (CAMTA3) protein in induction of RSRE was reaffirmed by genetic studies. Moreover, exogenous application of MeJA led to enhanced levels of ORA47 and CAMTA3 transcripts, and the induction of RSRE::LUC activity. Metabolic analyses illustrated the reciprocal functional inputs of ORA47 and CAMTA3 in increasing JA levels. Lastly, transient assays identified JASMONATE ZIM-domain1 (JAZ1) as a repressor of RSRE::LUC activity. Collectively, the report provides a fresh insight into the initial mechanistic features of transducing the informational signals into adaptive responses in part via the complex functional interplay between JA biosynthesis/signaling cascade and the transcriptional reprogramming necessary for potentiation of GSR, while offering a window into the role of intraorganellar communication in the establishment of adaptive responses. SignificanceThe work unmasks the initial mechanistic features of adaptive responses that include tight cooperativity between JA biosynthesis and signaling cascade and the nuclear transcriptional machinery comprised of two activators (CAMTA3 and ORA47) and a suppressor JAZ1). The work further identifies CAMTA3 as a functional link between JA signaling and activation of a general stress transcriptional hub.

plant biology↗

Reciprocity between retrograde signal and putative metalloprotease reconfigures plastidial metabolism and structure

Reconfiguration of the plastidial proteome in response to environmental inputs is central to readjustment of its metabolic and structural states. This is necessary for the functionality of this metabolic hub, and the maintenance of organismal integrity. This report establishes the role of the plastidial retrograde signaling metabolite, MEcPP, in increasing the abundance of the putative plastidial metalloprotease (VIR3), and the ensuing decline of VIR3 target enzymes, ascorbate peroxidase and glyceraldehyde 3-phophate dehydrogenase B. The decreased abundance of these enzymes is linked to increased levels of their substrates: H2O2, an elicitor of salicylic acid production and stromule formation; and G3P the substrate for MEcPP synthesis. High-light treatment of wild type plants recapitulated the VIR3-associated reconfiguration of the plastidial metabolic and structural states. These results identify a previously unrecognized link between the stress-induced plastidial retrograde signaling metabolite and a putative zinc-binding metalloprotease. Moreover, the data reveal that the reciprocity between these two components, results in the reconfiguration of the metabolic and structural states of the plastid, deemed necessary to maintain cellular integrity and to shape adaptive responses.

plant biology↗

Plasmodium falciparum vacuolar pyrophosphatase 1 for ring stage development and its transition to trophozoite

The malaria parasite relies on anaerobic glycolysis for energy supply when growing inside RBCs as its mitochondrion does not produce ATP. The ring stage lasts [~] 22 hours and is traditionally thought to be metabolically quiescent. However, recent studies show that the ring stage is active for several energy-costly processes including gene transcription/translation, protein export, and movement inside the RBC. It has remained unclear if a low glycolytic flux can meet the energy demand of the ring stage. Here we show that the metabolic by-product, pyrophosphate, is a critical energy source for the development of the ring stage and its transition to the trophozoite stage. During early phases of the asexual development, the parasite utilizes Plasmodium falciparum vacuolar pyrophosphatase 1 (PfVP1), an ancient pyrophosphate-driven proton pump, to pump protons across the parasite plasma membrane to maintain the membrane potential and cytosolic pH. Conditional deletion of PfVP1 leads to delayed ring stage development and a complete blockage of the ring-to-trophozoite transition, which can be partially rescued by Arabidopsis thaliana vacuolar pyrophosphatase 1, but not by the soluble pyrophosphatase from Saccharomyces cerevisiae. Proton-pumping pyrophosphatases are absent in humans, which highlights the possibility of developing highly selective VP1 inhibitors against the malaria parasite.

microbiology↗

A new Mendelian Randomization method to estimate causal effects of multivariable brain imaging exposures

The advent of simultaneously collected imaging-genetics data in large study cohorts provides an unprecedented opportunity to assess the causal effect of brain imaging traits on externally measured experimental results (e.g., cognitive tests) by treating genetic variants as instrumental variables. However, classic Mendelian Randomization methods are limited when handling high-throughput imaging traits as exposures to identify causal effects. We propose a new Mendelian Randomization framework to jointly select instrumental variables and imaging exposures, and then estimate the causal effect of multivariable imaging data on the outcome. We validate the proposed method with extensive data analyses and compare it with existing methods. We further apply our method to evaluate the causal effect of white matter microstructure integrity on cognitive function. The findings suggest that our method achieved better performance regarding sensitivity, bias, and false discovery rate compared to individually assessing the causal effect of a single exposure and jointly assessing the causal effect of multiple exposures without dimension reduction. Our application results indicated that WM measures across different tracts have a joint causal effect that significantly impacts the cognitive function among the participants from the UK Biobank.

bioinformatics↗

A plastidial retrograde-signal potentiates biosynthesis of systemic stress response activators

O_LIPlants employ an array of intricate and hierarchical signaling cascades to perceive and transduce informational cues to synchronize and tailor adaptive responses. Systemic stress response (SSR) is a recognized complex signaling and response network quintessential to plants local and distal responses to environmental triggers, however, the identity of the initiating signals has remained fragmented. C_LIO_LIHere, we show that both biotic (aphids and viral pathogens) and abiotic (high-light and wounding) stresses induce accumulation of the plastidial-retrograde-signaling metabolite, methylerythritol cyclodiphosphate (MEcPP), leading to reduction of the phytohormone, auxin, and the subsequent decreased expression of the phosphatase, PP2C.D1. C_LIO_LIThis enables phosphorylation of mitogen-activated protein kinases (MAPK3/6), and the consequential induction of the downstream events ultimately resulting in biosynthesis of the two SSR priming metabolites, pipecolic- and N-hydroxy-pipecolic acid. C_LIO_LIThis work identifies plastids as the initiation site, and the plastidial retrograde-signal, MEcPP as the initiator of a multi-component signaling cascade potentiating the biosynthesis of SSR activators, in response to biotic and abiotic triggers. C_LI

plant biology↗

RFRSN: Improving protein fold recognition by siamese network

Protein fold recognition is the key to study protein structure and function. As a representative pattern recognition task, there are two main categories of approaches to improve the protein fold recognition performance: 1) extracting more discriminative descriptors, and 2) designing more effective distance metrics. The existing protein fold recognition approaches focus on the first category to finding a robust and discriminative descriptor to represent each protein sequence as a compact feature vector, where different protein sequence is expected to be separated as much as possible in the fold space. These methods have brought huge improvements to the task of protein fold recognition. However, so far, little attention has been paid to the second category. In this paper, we focus not only on the first category, but also on the second point that how to measure the similarity between two proteins more effectively. First, we employ deep convolutional neural network techniques to extract the discriminative fold-specific features from the potential protein residue-residue relationship, we name it SSAfold. On the other hand, due to different feature representation usually subject to varying distributions, the measurement of similarity needs to vary according to different feature distributions. Before, almost all protein fold recognition methods perform the same metrics strategy on all the protein feature ignoring the differences in feature distribution. This paper presents a new protein fold recognition by employing siamese network, we named it PFRSN. The objective of PFRSN is to learns a set of hierarchical nonlinear transformations to project protein pairs into the same fold feature subspace to ensure the distance between positive protein pairs is reduced and that of negative protein pairs is enlarged as much as possible. The experimental results show that the results of SSAfold and PFRSN are highly competitive.

bioinformatics↗

ER exit sites in Drosophila display abundant ER-Golgi vesicles and pearled tubes but no megacarriers

Secretory cargos are collected at ER exit sites (ERES) before transport to the Golgi apparatus. Decades of research have provided many details of the molecular events underlying ER-Golgi exchanges. Essential questions, however, remain about the organization of the ER-Golgi interface in cells and the type of membrane structures mediating traffic from ERES. To investigate these, we used transgenic tagging in Drosophila flies, 3D-SIM and FIB-SEM to characterize ERES-Golgi units in collagen-producing fat body, imaginal discs and imaginal discs overexpressing ERES determinant Tango1. We found in front of ERES a pre-cis-Golgi region involved in both anterograde and retrograde transport. This pre-cis-Golgi is continuous with the rest of the Golgi, not a separate intermediate compartment or collection of large carriers, for which we found no evidence. We found, however, many vesicles, as well as pearled tubules connecting ERES and Golgi.

cell biology↗

Recombinant SARS-CoV-2 RBD molecule with a T helper epitope as a built in adjuvant induces strong neutralization antibody response

Without approved vaccines and specific treatment, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is spreading around the world with above 20 million COVID-19 cases and approximately 700 thousand deaths until now. An efficacious and affordable vaccine is urgently needed. The Val308 - Gly548 of Spike protein of SARS-CoV-2 linked with Gln830 - Glu843 of Tetanus toxoid (TT peptide) (designated as S1-4) and without TT peptide (designated as S1-5), and prokaryotic expression, chromatography purification and the rational renaturation of the protein were performed. The antigenicity and immunogenicity of S1-4 protein was evaluated by Western Blotting (WB) in vitro and immune responses in mice, respectively. The protective efficiency of it was measured by virus neutralization test in Vero E6 cells with SARS-CoV-2. S1-4 protein was prepared to high homogeneity and purity by prokaryotic expression and chromatography purification. Adjuvanted with Alum, S1-4 protein stimulated a strong antibody response in immunized mice and caused a major Th2-type cellular immunity compared with S1-5 protein. Furthermore, the immunized sera could protect the Vero E6 cells from SARS-CoV-2 infection with neutralization antibody GMT 256. The candidate subunit vaccine molecule could stimulate strong humoral and Th1 and Th2-type cellular immune response in mice, giving us solid evidence that S1-4 protein could be a promising subunit vaccine candidate.

bioengineering↗

Conservation of the Toxoplasma conoid proteome in Plasmodium reveals a cryptic conoid feature that differentiates between blood- and vector-stage zoite

The apical complex is the instrument of invasion used by apicomplexan parasites, and the conoid is a conspicuous feature of this apparatus found throughout this phylum. The conoid, however, is believed to be heavily reduced or missing from Plasmodium species and other members of the class Aconoidasida. Relatively few conoid proteins have previously been identified, making it difficult to address how conserved this feature is throughout the phylum, and whether it is genuinely missing from some major groups. Moreover, parasites such as Plasmodium species cycle through three invasive forms and there is the possibility of differential presence of the conoid between these stages. We have applied spatial proteomics and high-resolution microscopy to develop a more complete molecular inventory and understanding of the organisation of conoid-associated proteins in the model apicomplexan Toxoplasma gondii. These data revealed molecular conservation of all conoid substructures throughout Apicomplexa, including Plasmodium, and even in allied Myzozoa such as Chromera and dinoflagellates. We reporter-tagged and observed the expression and location of several conoid complex proteins in the malaria model P. berghei and revealed equivalent structures in all of its zoite forms, as well as evidence of molecular differentiation between blood-stage merozoites and the ookinetes and sporozoites of the mosquito vector. Collectively we show that the conoid is a conserved apicomplexan element at the heart of the invasion mechanisms of these highly successful and often devastating parasites.

cell biology↗

A dispensable role of mitochondrial fission protein 1 (Fis1) in the erythrocytic development of Plasmodium falciparum

Malaria remains a huge global health burden and control of this disease has run into a severe bottleneck. To defeat malaria and reach the goal of eradication, a deep understanding of parasite biology is urgently needed. The mitochondrion of the malaria parasite is essential throughout the parasites lifecycle and has been validated as a clinical drug target. In the asexual development of Plasmodium spp., the single mitochondrion grows from a small tubular structure to a complex branched network. At the end of schizogony when 8-32 merozoites are produced, the branched mitochondrion is precisely divided, distributing one mitochondrion to each forming daughter merozoite. In mosquito and liver stages, the giant mitochondrial network is split into thousands of pieces then daughter mitochondria are segregated into individual progeny. Despite the significance of mitochondrial fission in Plasmodium, the underlying mechanism is largely unknown. Studies of mitochondrial fission in model eukaryotes have revealed that several mitochondrial fission adaptor proteins are involved in recruiting dynamin GTPases to physically split mitochondrial membranes. Apicomplexan parasites, however, share no identifiable homologs of mitochondrial fission adaptor proteins of yeast or human, except for Fis1. Here, we investigated the localization and essentiality of the Fis1 homolog in Plasmodium falciparum, PfFis1 (PF3D7_1325600), during the asexual lifecycle. We found that PfFis1 requires an intact C-terminus for mitochondrial localization but is not essential for parasite development or mitochondrial fission. The dispensable role of PfFis1 indicates Plasmodium contains additional fission adaptor proteins on the mitochondrial outer membrane that could be essential for mitochondrial fission. ImportanceMalaria is responsible for over 230 million clinical cases and [~] half a million deaths each year. The single mitochondrion of the malaria parasite functions as a metabolic hub throughout the parasites developmental cycle as well as a source of ATP in certain stages. To pass on its essential functions, the parasites mitochondrion needs to be properly divided and segregated into all progeny during cell division via a process named mitochondrial fission. Due to the divergent nature of Plasmodium spp., molecular players involved in mitochondrial fission and their mechanisms of action remain largely unknown. We found that Fis1, the only identifiable mitochondrial fission adaptor protein evolutionarily conserved in the phylum of Apicomplexa, however, is not essential for Plasmodium falciparum. Our data suggest that malaria parasites use redundant fission adaptor proteins on the mitochondrial outer membrane to mediate the fission process.

biochemistry↗

A subcellular atlas of Toxoplasma reveals the functional context of the proteome

Apicomplexan parasites cause major human disease and food insecurity. They owe their considerable success to novel, highly specialized cell compartments and structures. These adaptations drive their recognition and non-destructive penetration of hosts cells and the elaborate reengineering of these cells to promote growth, dissemination, and the countering of host defenses. The evolution of unique apicomplexan cellular compartments is concomitant with vast proteomic novelty that defines these new cell organizations and their functions. Consequently, half of apicomplexan proteins are unique and uncharacterized, and these cells are, therefore, very poorly understood. Here, we determine the steady-state subcellular location of thousands of proteins simultaneously within the globally prevalent apicomplexan parasite Toxoplasma gondii. This provides unprecedented comprehensive molecular definition to these cells and their novel compartments, and these data reveal the spatial organizations of protein expression and function, adaptation to hosts, and the underlying evolutionary trajectories of these pathogens.

cell biology↗

Retrograde induction of phyB orchestrates ethylene-auxin hierarchy to regulate growth

Exquisitely regulated plastid-to-nucleus communication by retrograde signaling pathways is essential for fine-tuning of responses to the prevailing environmental conditions. The plastidial retrograde signaling metabolite methylerythritol cyclodiphosphate (MEcPP) has emerged as a stress signal transduced into a diverse ensemble of response outputs. Here we demonstrate enhanced phytochrome B protein abundance in red-light grown MEcPP-accumulating mutant (ceh1) plant relative to wild-type seedlings. We further establish MEcPP-mediated coordination of phytochrome B with auxin and ethylene signaling pathways, and uncover differential hypocotyl growth of red-light grown seedlings in response to these phytohormones. Genetic and pharmacological interference with ethylene and auxin pathways outline the hierarchy of responses, placing auxin epistatic to the ethylene signaling pathway. Collectively, our finding establishes the key role of a plastidial retrograde metabolite in orchestrating the transduction of a repertoire of signaling cascades, and positions plastids at the zenith of relaying information coordinating external signals and internal regulatory circuitry to secure organismal integrity. Two sentence summaryThe plastidial retrograde metabolite, MEcPP, orchestrates coordination of light and hormonal signaling cascade through induction of phytochrome B abundance and modulation of auxin and ethylene levels for optimal adaptive responses to light environment.

plant biology↗

Genetic ablation of the mitochondrial ribosome in Plasmodium falciparum sensitizes the human malaria parasite to antimalarial drugs targeting mitochondrial functions

The mitochondrion of malaria parasites contains clinically validated drug targets. Within Plasmodium spp., the mitochondrial DNA (mtDNA) is only 6 kb long, being the smallest mitochondrial genome among all eukaryotes. The mtDNA encodes only three proteins of the mitochondrial electron transport chain and [~] 27 small, fragmented rRNA genes in length of 22-195 nucleotides. The rRNA fragments are thought to form a mitochondrial ribosome (mitoribosome), together with ribosomal proteins imported from the cytosol. The mitoribosome of Plasmodium falciparum has been shown to be essential for maintenance of the mitochondrial membrane potential and parasite viability. However, the role of mitoribosomes in sustaining the metabolic status of the parasite mitochondrion remains unknown. Here, among the 14 annotated mitoribosomal proteins of the small subunit of P. falciparum, we verified the localization and tested the essentiality of three candidates (PfmtRPS12, PfmtRPS17, PfmtRPS18), employing a CRISPR/Cas9 mediated conditional knockdown tool. Using immuno-electron microscopy, we provided evidence that the mitoribosome is closely associated with the mitochondrial inner membrane in the parasite. Upon knockdown of the mitoribosome, the parasites became hypersensitive to inhibitors targeting the bc1 complex, dihydroorotate dehydrogenase and F1Fo ATP synthase complex. Furthermore, knockdown of the mitoribosome blocked the pyrimidine biosynthesis pathway and reduced the pool of pyrimidine nucleotides. Together, our data suggest that disruption of the P. falciparum mitoribosome compromises the metabolic capability of the mitochondrion, rendering the parasite hypersensitive to a panel of inhibitors targeting mitochondrial functions.

biochemistry↗

DHH1/DDX6-like RNA helicases maintain ephemeral half-lives of stress-response mRNAs associated with innate immunity and growth inhibition

Gene transcription is counterbalanced by mRNA decay processes that regulate transcript quality and quantity. We show here that the evolutionarily conserved DHH1/DDX6-like RNA HELICASEs of Arabidopsis thaliana control the ephemerality of a subset of cellular mRNAs. These RNA helicases co-localize with key markers of processing bodies and stress granules and contribute to their subcellular dynamics. These RHs function to limit the precocious accumulation and translation of stress-responsive mRNAs associated with autoimmunity and growth inhibition under non-stress conditions. Given the conservation of this RH subfamily, they may control basal levels of conditionally-regulated mRNAs in diverse eukaryotes, accelerating responses without penalty.

plant biology↗