Genome-wide identification of the basic leucine zipper transcription factor genes related to starch synthesis in wheat (Triticum aestivum L.)

In plants, the basic leucine zipper (bZIP) family of transcription factors is known for its large size and diversity. Many studies have shown that bZIP transcription factors play an indispensable role in the growth and development of plants; however, there are few reports about the regulation of starch content in grain. To understand the genetic members of the bZIP family, using newly available wheat genome data, we compared our identification of 181 Triticum aestivum bZIP (TabZIP) genes to those reported in earlier studies. Some duplicate genes and incorrect annotations in previous studies were supplemented and corrected. Through phylogenetic analysis, transcriptome data, quantitative reverse transcription PCR (qRT-PCR), a dual-luciferase reporter (DLR), and subcellular localization analysis were used to identify transcription factors that may be involved in grain starch synthesis. We divided genes into 13 known groups and five unknown groups by phylogenetic analysis. All of the bZIP genes exhibited a minimum of one bZIP motif in their motif distribution and gene structure. Spatial and temporal expression patterns of bZIP family members during various stages of plant growth vary, as suggested by transcriptome data, and several genes were specifically expressed during grain development. As per the expression data obtained via qRT-PCR, over 10 TabZIP genes showed similarity with starch synthesis in wheat. The in-vitro binding activity of TabZIP68 to the promoter of TaWaxy was demonstrated by a DLR assay. Expression level of TabZIP68 was affected by different plant hormones treated with developing grains. Given its potential involvement in starch synthesis, the TabZIP68 gene presents itself as a strong candidate for further investigation.