Zm MYB 14 is an important transcription factor involved in the regulation of the activity of the Zm BT 1 promoter in starch biosynthesis in maize

Abstract

The biosynthesis of starch is a complex process that depends on the regulatory mechanisms of different functional enzymes, and transcriptional regulation plays an important role in this process. Brittle 1, encoded by BT 1 , is a transporter of adenosine diphosphate‐glucose, which plays an important role in the biosynthesis of starch in the endosperm of cereals. Here, we report that the promoter ( pZmBT 1 ) of the maize BT 1 homolog, Zm BT 1 , contains an MBSI site ( TAACTG ), which is important for its activity. Moreover, high expression level of the gene for Zm MYB 14 transcription factor was observed in the maize endosperm; its expression pattern was similar to those of the starch synthesis‐related genes in maize seeds. Zm MYB 14 is a typical 2R‐ MYB transcription factor localized in the nucleus and possessed transcriptional activation activity. Zm MYB 14 could bind to the region of pZmBT 1 from −280 to −151 bp and promote its activity through the TAACTG site. It was also observed to promote the activity of pZmS h2 , pZmB t2 , pZmGBSSI , pZmSSI , and pZmSBE 1 in the maize endosperm in transient gene overexpression assays. Furthermore, Zm MYB 14 was also shown to bind directly to the promoters of six starch‐synthesizing genes, Zm GBSSI , Zm SSI , Zm SSII a , Zm SBE 1 , Zm ISA 1 , and Zm ISA 2 in yeast. These findings indicate that Zm MYB 14 functions as a key regulator of Zm BT 1 and is closely related to the biosynthesis of starch. Our results provide crucial information related to the regulation of starch biosynthesis in maize and would be helpful in devising strategies for modulating starch production in maize endosperm.