Phylogenetic analysis of NAC gene family in grain Sorghum and expression pattern analysis of drought responsive members

Sorghum, in spite of its great tolerance to drought stress, suffers from grain yield loss due to pre and post flowering -drought stress conditions. NAC TFs play key roles in Sorghum drought adaptation. In this study, NAC protein family data was collected from databases. Then, hidden Markov model profiles of NAM domain (PF02365) was obtained from Pfam database and used to find the putative NAC members against Sorghum proteins. Totally, 183 protein sequences encoded by 131 gene loci were identified. The unrooted phylogenetic tree was constructed based on NAC domains of Sorghum and 11 known NAC domains of other plants using the Neighbor-Joining method, which classified the family into 15 subfamilies. 13 members of the NAC protein family of Sorghum joined to the SNAC subfamily of other plants, which are expected to be involved in abiotic stress tolerance. 14 different stress and hormone responsive regulatory elements were predicted in promoters of SNAC subgroupgenes. To study the expression pattern of these genes, two extreme Sorghum cultivars including Kimia and Sepideh were planted based on Split-plot Randomized Complete Block Design with three replications in the field. Irrigation was performed in two levels including normal irrigation and drought stress (water holding from anthesis). Based on the SbSNAC expression pattern, we predict that some members are involved in response to drought stress at post-flowering stage as positive (3 members) and negative transcriptional regulators (3 members). As well, some of them play role in leaf senescence (2 members) and metal remobilization processes (2 members).