Biology subjects

Attia, Z.

Publications and source records attributed to Attia, Z..

6 recordsLinked to original sources

bioRxiv2024

Environment, plant genetics, and their interaction shape important aspects of sunflower rhizosphere microbial communities

Associations with soil microorganisms are crucial for plants overall health and functioning. While much work has been done to understand drivers of rhizosphere microbiome structure and function, the relative importance of geography, climate, soil properties, and plant genetics remains unclear, as results have been mixed and comprehensive studies across many sites and genotypes are limited. Rhizosphere microbiomes are crucial for crop resistance to pathogens, stress tolerance, nutrient availability, and ultimately yield. Here we quantify the relative roles of plant genotype, environment, and their interaction in shaping soil rhizosphere communities, using 16S and ITS gene sequencing of rhizosphere soils from 10 common sunflower (Helianthus annuus) genotypes from 15 sites across the Great Plains of the United States. While site generally outweighed genotype overall in terms of effects on archaeal, bacterial and fungal richness, community composition, and taxa relative abundances, there was also a significant interaction such that genotype exerted a significant influence on archaeal, bacterial and fungal microbiomes in certain sites. Site effects were attributed to a combination of spatial distance and differences in climate and soil properties. Microbial taxa that were previously associated with resistance to the fungal necrotrophic pathogen Sclerotinia were present in most sites but differed significantly in relative abundance across sites. Our results have implications for plant breeding and agronomic microbiome manipulations for agricultural improvement across different geographic regions. ImportanceDespite the importance of plant breeding in agriculture, we still have a limited understanding of how plant genetic variation shapes soil microbiome composition across broad geographic regions. Using 15 sites across the Great Plains of North America, we show that cultivated sunflower rhizosphere archaeal, bacterial and fungal communities are driven primarily by site soil and climatic differences, but that genotype can interact with site to influence composition, especially in warmer and drier sites with lower overall microbial richness. We also show that all taxa that were previously found to be associated with resistance to the fungal pathogen Sclerotinia sclerotiorum were widespread but significantly affected by site, while a subset were also significantly affected by genotype. Our results contribute to a broader understanding of rhizosphere archaeal, bacterial and fungal community assembly, and provide foundational knowledge for plant breeding efforts and potential future microbiome manipulations in agriculture.

ecology↗

bioRxiv2021

Revealing the genetic components responsible for the unique photosynthetic stem capability of the wild almond Prunus arabica (Olivier) Meikle

Almond (Prunus dulcis (Mill.) D. A. Webb) is a major deciduous fruit tree crop worldwide. During dormancy, under warmer temperatures and inadequate chilling hours, the plant metabolic activity increases and may lead to carbohydrate deficiency. Prunus arabica (Olivier) Meikle is a bushy wild almond species known for its green, un-barked stem, which stays green even during the dormancy period. Our study revealed that P. arabica green stems assimilate significantly high rates of CO2 during the winter as compared to P. dulcis cv. Um el Fahem (U.E.F), and may improve carbohydrate status throughout dormancy. To uncover the genetic inheritance and mechanism behind the P. arabica Stem Photosynthetic Capability (SPC), a segregated F1 population was generated by crossing P. arabica to U.E.F. Both parents whole genome was sequenced, and a single nucleotide polymorphism (SNP) calling identified 4,887 informative SNPs for genotyping. A robust genetic map for U.E.F and P. arabica was constructed (971 and 571 markers, respectively). QTL mapping and association study for the SPC phenotype revealed major QTL (log of odd (LOD)=20.8) on chromosome 7, and another minor but significant QTL on chromosome 1 (LOD=3.9). Finally, a list of 73 candidate genes was generated. This work sets the stage for future research to investigate the mechanism regulating the SPC trait, how it affects the trees physiology, and its importance for breeding new cultivars better adapted to high winter temperatures.

plant biology↗

bioRxiv2021

Flagellin triggers mesophyll dehydration: An early PTI defense against bacterial establishment in intercellular spaces

Plants have evolved various mechanisms to defend themselves against pathogens. Many pathogens induce the formation of water-soaked lesions during early infection under conditions of high atmospheric humidity. These water-soaked spots are caused by the disruption of the plasma membrane or cell wall integrity due to various activities of effector proteins during infection. We hypothesized that bacterial PAMP-flagellin plays a role in modulating the cell-membrane permeability that controls the availability of water in the apoplast, to prevent bacterial establishment on the cell wall during the early stages of the PAMP-triggered immunity (PTI) response. Our results revealed that the conductivity of hydraulic pathways in the leaf was reduced in response to flagellin22 (flg22). The cellular osmotic water permeability (Pf) of both mesophyll cells and bundlesheath cells was dramatically reduced in response to flg22 treatment. Moreover, the whole-leaf hydraulic conductance (Kleaf) was also reduced in response to flg22 treatment. The fact that the Pf of mesophyll cells of an aquaporin (AQP) mutant was not affected by the flg22 treatment suggests the involvement of AQP channels in the flg22-induced Pf reduction signal transduction pathway. We conclude that the binding of flagellin to their receptors elicits signals to close AQPs, consequently reducing the water content of the cell wall and intercellular spaces and leading to a more negative water potential. This serves as an early PTI response to pathogen attack, which, in turn, might decrease the rate of bacterial growth and establishment in the apoplast. Significance statementWe report that the membrane osmotic water permeability of both leaf mesophyll and vascular bundle-sheath cells is reduced in response to treatment with flagellin22. We suggest that this mechanism for cell dehydration may serve as an apoplastic defense response, to limit the chances of bacterial pathogens becoming established on the walls of leaf mesophyll cells.

plant biology↗

bioRxiv2020

Heritable associations with microbial communities are essential for necrotrophic pathogen resistance

Host-microbe interactions are increasingly recognized as important drivers of organismal health, growth, longevity, and community-scale ecological processes. However, less is known about how genetic variation affects hosts associated microbiomes and downstream phenotypes. We demonstrate that sunflower (Helianthus annuus) harbors substantial, heritable variation in microbial communities under field conditions. We show that microbial communities explain up to 77.5% of the heritable variation in resistance to root infection caused by the necrotrophic pathogen Sclerotinia sclerotiorum, and that plants grown in sterilized soil showed almost complete elimination of pathogen resistance. Association mapping revealed 69 genetic locations related to microbial abundance and Sclerotinia resistance. Although the genetic architecture is complex and quantitative, we have, in large part, elucidated previously unexplained genetic variation for resistance to this pathogen. This suggests new targets for plant breeding and demonstrates the potential for heritable microbial associations to play important roles in defense in natural and human-altered environments.

ecology↗

bioRxiv2020

A High Throughput Gravimetric Phenotyping Platform for Real Time Physiological Screening of Plant Environment Dynamic Responses

Food security for the growing global population is a major concern. The data provided by genomic tools far exceeds the supply of phenotypic data, creating a knowledge gap. To meet the challenge of improving crops to feed the growing global population, this gap must be bridged. Physiological traits are considered key functional traits in the context of responsiveness or sensitivity to environmental conditions. Many recently introduced high-throughput phenotyping techniques are based on remote sensing or imaging and are capable of directly measuring morphological traits, but measure physiological parameters only indirectly. This paper describes a method for direct physiological phenotyping that has several advantages for the functional phenotyping of plant-environment interactions. It aims to help users overcome the many challenges encountered in the use of load-cell gravimetric systems and pot experiments. The suggested techniques will enable users to distinguish between soil weight, plant weight and soil water content, providing a method for continuous and simultaneous measurement of dynamic soil, plant and atmosphere conditions, alongside key physiological traits. This method allows researchers to closely mimic field stress scenarios while taking into consideration the environments effect on the plants physiology. This method also minimizes pot effects, which are one of the major problems in pre-field phenotyping. It includes a feedback fertigation system that enables a truly randomized experimental design with a field-like plant density. This system detects the soil-water content limiting threshold ({theta}) and allows for the translation of data into knowledge through the use of a real-time analytic tool and an online statistical resource. This method for the rapid and direct measurement of the physiological responses of multiple plants to a dynamic environment has great potential for use in screening for beneficial traits associated with responses to abiotic stress, in the context of pre-field breeding and crop improvement. SUMMARYThis high-throughput, whole-plant water relations gravimetric phenotyping method enables direct and simultaneous real-time measurements and analysis of multiple yield-related physiological traits involved in dynamic plant-environment interactions.

plant biology↗

bioRxiv2018

Vascular bundle sheath and mesophyll regulation of leaf water balance in response to chitin

Plants can detect pathogen invasion by sensing pathogen-associated molecular patterns (PAMPs). This sensing process leads to the induction of defense responses. Most PAMP mechanisms of action have been described in the guard cells. Here, we describe the effects of chitin, a PAMP found in fungal cell walls, on the cellular osmotic water permeability (Pf) of the leaf vascular bundle-sheath (BS) and mesophyll cells and its subsequent effect on leaf hydraulic conductance (Kleaf).\n\nThe BS is a parenchymatic tissue that tightly encases the vascular system. BS cells have been shown to control Kleaf through changes in their Pf, for example, in response to ABA. It was recently reported that, in Arabidopsis, the chitin receptors chitin elicitor receptor kinase 1 (CERK1) and LYSINE MOTIF RECEPTOR KINASE 5 (LYK5) are highly expressed in the BS, as well as the neighboring mesophyll. Therefore, we studied the possible impact of chitin on these cells.\n\nOur results revealed that both BS cells and mesophyll cells exhibit a sharp decrease in Pf in response to chitin treatment. In addition, xylem-fed chitin decreased Kleaf and led to stomatal closure. However, an Atlyk5 mutant showed none of these responses. Complimenting AtLYK5 specifically in the BS cells (using the SCARECROW promoter) and transient expresion in mesophyll cells each resulted in a response to chitin that was similar to that observed in the wild type. These results suggest that BS and mesophyll cells each play a role in the perception of apoplastic chitin and in initiating chitin-triggered immunity.\n\nSignificance StatementPAMP perception by plant receptors triggers various defense responses important for plant immunity. Here we provide new insights into a topic that has received a great deal of previous attention, revealing that a chitin immune response is present in additional leaf tissues other than the stomata. Chitin perception by the bundle sheath cells enwrapping the whole leaf vascular system decrease its cellular osmotic permeability and leaf hydraulic conductance. This in turn, leads to hydraulic signals being sent to the stomata and regulates whole-leaf water balance in response to chitin application and, perhaps, during fungal infection. Emphasizing the dynamic role of the BS in chitin-sensing and water balance regulation.

plant biology↗