Arabidopsis NDL-AGB1 modules Play Role in Abiotic Stress and Hormonal Responses Along with Their Specific Functions

Arabidopsis N-MYC Downregulated Like Proteins (NDLs) are interacting partners of G-Protein core components. Animal homologs of the gene family N-myc downstream regulated gene (NDRG) has been found to be induced during hypoxia, DNA damage, in presence of reducing agent, increased intracellular calcium level and in response to metal ions like nickel and cobalt, which indicates the involvement of the gene family during stress responses. Arabidopsis NDL gene family contains three homologs NDL1, NDL2 and NDL3 which share up to 75% identity at protein level. Previous studies on NDL proteins involved detailed characterization of the role of NDL1; roles of other two members were also established in root and shoot development using miRNA knockdown approach. Role of entire family in development has been established but specific functions of NDL2 and NDL3 if any are still unknown. Our in-silico analysis of NDLs promoters reveled that all three members share some common and some specific transcription factors (TFs) binding sites, hinting towards their common as well as specific functions. Based on promoter elements characteristics, present study was designed to carry out comparative analysis of the Arabidopsis NDL family during different stages of plant development, under various abiotic stresses and plant hormonal responses, in order to find out their specific and combined roles in plant growth and development. Developmental analysis using GUS fusion revealed specific localization/expression during different stages of development for all three family members. Stress analysis after treatment with various hormonal and abiotic stresses showed stress and tissue-specific differential expression patterns for all three NDL members. All three NDL members were collectively showed role in dehydration stress along with specific responses to various treatments. Their specific expression patterns were affected by presence of interacting partner the Arabidopsis heterotrimeric G-protein β subunit 1 (AGB1). The present study will improve our understanding of the possible molecular mechanisms of action of the independent NDL–AGB1 modules during stress and hormonal responses. These findings also suggest potential use of this knowledge for crop improvement.