Protein protein interaction network study of shoot stem cell niche derived transcription factors revealed the contrasting roles of Elongated Hypocotyl 5 and Dewax in UV B stress in Arabidopsis thaliana

Abstract

The shoot apical meristems (SAMs) consist of a small population of stem cells surrounded by newlineproliferating cells that differentiate into distinct cell types to generate aerial parts of the plant. newlineThe specification of these cell-types and fates involves complex gene regulatory networks that newlineare primarily regulated by transcription factors (TFs). Despite four decades of intensive genetic newlineresearch, our understanding of transcriptional gene networks remains poor and deciphering newlinethem is vital for understating SAM development in plants. newlineIn this study, I identified the TFs that are enriched in stem cells and surrounding cell types and newlinegenerated a high-resolution protein-protein interaction (PPI) map using high throughput yeast- newlinetwo-hybrid (Y2H) assay. I checked more than 3000 interactions among 71 TFs enriched in the newlineshoot apical meristem. I found 413 positive interactions, which are supported both by co- newlineexpression and co-occurrence, allowing me to produce a highly robust and reproducible protein newlineinteraction map of cell-type enriched TFs. I also tried to dissect the genetic roles of these TFs newlinein plant development by looking at the knockout and overexpression. I found out that the plants newlineoverexpressing the previously uncharacterized gene AT4G16610 exhibit dwarfism along newlinewith petite flowers, showing abnormalities in most floral organs. The carpels had a newlinetendency to protrude out from developing buds and resembled the shape of a whirligig, and newlinehence, I gave the name WHIRLIGIG to this locus.Based on the PPI network, I identified AtMYB4 as a hub. It is known as one of the key newlineregulators of anthocyanin production during UV-B stress, and it is enriched in the epidermal newlinelayer of SAM. A screen conducted on the SAM epidermal cell-type enriched TF mutants newlinerevealed the role of DEWAX in UV-B tolerance. The dewax mutants were highly tolerant to newlineUV-B stress while the plants overexpressing DEWAX showed enhanced sensitivity to UV-B newlinestress and exhibited 100% mortality.