Tran, L.-S. P. | Search bioRxiv

bioRxiv2024

Iron-induced Transcriptional and Microbiome Changes in Host Roots Associated with Drought Tolerance in Sorghum

Drought stress significantly impairs growth, and microbial interactions in sorghum. This study explores the transcriptional and microbial shifts in sorghum under drought, revealing key adaptations to water deficit. LC-MS (Liquid Chromatography-Mass Spectrometry) analyses revealed that drought stress induced abscisic acid while significantly reducing jasmonic acid levels in sorghum roots, likely due to resource conservation strategies during drought. Transcriptional reprogramming highlighted the upregulation of genes in the roots involved in mineral homeostasis (Ferritin 1, Iron dehydrogenase, Nitrate transporter 1), hormone signaling (Ethylene-insensitive protein 3, Gibberellin 2-oxidase), and osmotic regulation (Aquaporin, Dehydrin), underlining key adaptive responses to maintain nutrient uptake, redox status, and cellular turgor. In Fe-supplemented plants, increased Fe in roots correlated with increased Ferritin 1 expression, improved plant health, and reduced Fenton reaction rate and H O levels. This suggests that ferritin helps minimize oxidative stress under drought in sorghum. Drought reduced root-associated bacterial diversity and richness while enriching drought tolerance-associated genera, such as Burkholderia, Caballeronia and Paraburkholderia, known for promoting plant growth through auxin production, phosphate solubilization, and siderophore-mediated iron acquisition. In contrast, fungal diversity and richness remained unchanged, dominated by Talaromyces, which showed a statistically non-significant increase under drought. Random forest models could not identify functional predictors for fungi but revealed a shift in bacterial functional groups under drought, with enrichment in phototrophy, methylotrophy, and nitrate reduction, traits emphasizing microbial roles in nutrient cycling and drought adaptation of sorghum. This study provides insights into the role of ferritin and potential bacterial bioinoculants that could enhance sorghum resilience to drought. Future research should validate these findings to integrate them into breeding programs and biofertilizer formulation for drought-tolerant sorghum and climate-resilient agriculture.

plant biology↗

bioRxiv2022

Identification of two bZIP transcription factors that regulate development of pavement and trichome cells in Arabidopsis thaliana by single-cell RNA-sequencing

Epidermal cells are the main avenue for signal and material exchange between plants and the environment. Leaf epidermal cells primarily include pavement cells (PCs), guard cells, and trichomes cells (TCs), which differentiate from protodermal cells or meristemoids. The development and distribution of different epidermal cells are tightly regulated by a complex transcriptional regulatory network mediated by phytohormones, including jasmonic acid (JA), and transcription factors. Understanding how the fate of leaf epidermal cells is determined, however, is still largely unknown due to the diversity of cell types and the complexity of its regulation. Here, we characterized the transcriptional profiles of epidermal cells in 3-day-old true leaves of Arabidopsis thaliana using single-cell RNA-sequencing. We identified two genes encoding BASIC LEUCINE-ZIPPER (bZIP) transcription factors, namely the bZIP25 and bZIP53, which are highly expressed in PCs and early-stage meristemoid cells. Densities of PCs and TCs were found to increase and decrease, respectively, in bzip25 and bzip53 mutants, compared with wild-type plants. This trend was more pronounced in the presence of JA, suggesting that these transcription factors regulate the development of TCs and PCs in response to JA. IN A NUTSHELLO_ST_ABSBackgroundC_ST_ABSLeaf epidermal cells, comprised of trichome cells (TCs), guard cells (GCs), and pavement cells (PCs), are responsible for exchanging materials and information between plants and the surrounding aerial environment. Many genes have been identified in Arabidopsis thaliana and confirmed to be involved in the initiation and differentiation of TCs and PCs. The fate determination of TCs and PCs is tightly regulated by positive and negative regulators at the cellular level. The precise underlying molecular mechanisms responsible for the fate determination of TCs and PCs, however, are still unclear at this time. QuestionWhat are the transcriptomic profiles of different leaf epidermal cell types? Can we dissect the genes that are specifically expressed in certain epidermal cell types? What kinds of transcription factors are involved in regulating the fate determination of TCs and PCs? FindingsWe performed single cell RNA-seq to investigate the transcriptomic profiles of different leaf epidermal cell types and identified differentially expressed genes in each cell type. We found that genes that are involved in jasmonic acid signaling are highly expressed in early-stage meristemoid (EM) cells which can act as the precursor of PCs and perhaps of TCs. To investigate the regulatory mechanisms underlying EM development, we identified the transcription factors (TFs) in EM cells and found that two bZIP TF genes, bZIP25 and bZIP53, are highly expressed in EMs. Further analyses of these two genes using both loss-of-function and gain-of-function approaches indicated that bZIP25 and bZIP53 are functionally involved in promoting trichome formation but inhibit pavement cell development in response to jasmonic acid. Next stepsBesides of bZIP25 and bZIP53, we also identified other key genes, for example FES1B, in leaf epidermal cells. Our next step will be to explore the regulation of other key genes involved in the fate determination of different cell types in leaf epidermis.

plant biology↗