PPI Network Analysis for Differentially Expressed TFs
In the present study, 354, 348, 363 and 324 differentially expressed TFs were observed in DTL, DSL, DSP and DTP genotypes, respectively under drought stress. A total of 265 and 270 TFs were down-regulated in DSP and DSL, respectively, whereas 185 and 155 TFs were up-regulated in DTL and DTP, respectively (Table 4). Interestingly, the myriad of TFs, were down-regulated in sensitive genotypes (DSP & DSL) under stress (Table 3; Table S10). Most of the TFs were associated with MYB (myeloblastosis), bHLH (basic helix-loop-helix), ERF (Ethylene-responsive factor), NAC and WRKY families (Table 4).However, MYB represented the highest number of differentially expressed TFs followed by WRKY, ERF, bHLH and NAC under drought stress. To explore the interaction of drought related TFs, we constructed PPI network by using STRING. Among all the differentially expressed MYB genes, MYB127 and MYB184 showed highest and lowest expression level in tolerant and sensitive genotypes, respectively; similarly, MYB78 showed lowest expression in tolerant relative to sensitive genotypes. Hence, we checked separately the interaction of these three MYB genes with all other TFs to understand their PPI interaction with other differentially regulated TFs. Interestingly, all these three MYB genes were observed to act as hub gene interacting with the maximum number of nodes(Fig. 8). For example, MYB78 acting as a hub gene that interacts with NAC2, BZIP48, DREB1 and C2H2 (Fig. 8B ). Similarly, hub gene MYB184 interacts with WRKY25, BHLH and AP2 (Fig. 10C) . MYB127 interacts with MYB54 and MYB48, and showed highest level of expression among all MYB in tolerant genotype suggesting its positive role in drought tolerance (Fig. 8A).Hence, our results propose that MYB78, MYB127 and MYB184 genes might be the key elements of stress-related signaling networks.