Comparative transcriptome analyses revealed key genes involved in high amylopectin biosynthesis in wheat

High amylopectin starch is an important modified starch for food processing industries. Despite a thorough understanding of starch biosynthesis pathway, the regulatory mechanism responsible for amylopectin biosynthesis is not well explored. The present study utilized transcriptome sequencing approach to understand the molecular basis of high amylopectin content in three high amylopectin mutant wheat lines (‘TAC 6’, ‘TAC 358’, and ‘TAC 846’) along with parent variety ‘C 306’. Differential scanning calorimetry (DSC) of high amylopectin starch identified a high thermal transition temperature and scanning electron microscopy (SEM) revealed more spherical starch granules in mutant lines compared to parent variety. A set of 4455 differentially expressed genes (DEGs) were identified at two-fold compared to the parent variety in high amylopectin wheat mutants. At ten-fold, 279 genes, including two starch branching genes ( SBEIIa and SBEIIb ), were up-regulated and only 30 genes, including the starch debranching enzyme ( DBE ), were down-regulated. Among the genes, different isoforms of sucrose non-fermenting-1-related protein kinase-1 ( TaSnRK1α2 -3B and TaSnRK1α2 -3D) and its regulatory subunit, sucrose non-fermenting-4 ( SNF-4 -2A, SNF-4 -2B, and SNF-4 -5D), were found to be highly up-regulated. Further, expression of the DEGs related to starch biosynthesis pathway and TaSnRK1α2 and SNF-4 was performed using qRT-PCR. High expression of TaSnRK1α2 , SNF-4 , and SBEII isoforms suggests their probable role in high amylopectin starch biosynthesis in grain endosperm.