ZmbZIP91 regulates expression of starch synthesis-related genes by binding to ACTCAT elements in their promoters

Abstract

Starch synthesis is a key process that influences crop yield and quality, though little is known about the regulation of this complex metabolic pathway. Here, we present the identification of ZmbZIP91 as a candidate regulator of starch synthesis via co-expression analysis in maize (Zea mays L.). ZmbZIP91 was strongly associated with the expression of starch synthesis genes. Reverse tanscription-PCR (RT-PCR) and RNA in situ hybridization indicated that ZmbZIP91 is highly expressed in maize endosperm, with less expression in leaves. Particle bombardment-mediated transient expression in maize endosperm and leaf protoplasts demonstrated that ZmbZIP91 could positively regulate the expression of starch synthesis genes in both leaves and endosperm. Additionally, the Arabidopsis mutant vip1 carried a mutation in a gene (VIP1) that is homologous to ZmbZIP91, displayed altered growth with less starch in leaves, and ZmbZIP91 was able to complement this phenotype, resulting in normal starch synthesis. A yeast one-hybrid experiment and EMSAs showed that ZmbZIP91 could directly bind to ACTCAT elements in the promoters of starch synthesis genes (pAGPS1, pSSI, pSSIIIa, and pISA1). These results demonstrate that ZmbZIP91 acts as a core regulatory factor in starch synthesis by binding to ACTCAT elements in the promoters of starch synthesis genes.

Virus-Induced Gene Silencing Identifies an Important Role of the TaRSR1 Transcription Factor in Starch Synthesis in Bread Wheat

“…The RSR1 transcription factor belongs to the AP2 group of the AP2/EREBP family, which is characterized by an AP2 domain [20]. AP2/EREBP can recognize the GCAC(A/G)N(A/T)TCCC(A/G)ANG(C/T), DRE, GCC, JERE, CAACA, ACGT, and ACTCAT boxes in the promoters of target genes [38,42,43,44,45,46]. These boxes have been identified in the promoters of some upregulated starch synthesis-related enzyme genes in grains of BSMV-TaRSR1-infected wheat spikes.…”

“…These boxes have been identified in the promoters of some upregulated starch synthesis-related enzyme genes in grains of BSMV-TaRSR1-infected wheat spikes. For example, ACGT and ACTCAT boxes were found in the promoters of GBSSI and BEI genes of rice [38,45], and AGPS1 , SSI , SSIIIa , and ISA1 genes of maize, respectively [46]. Therefore, TaRSR1 may directly and negatively regulate the expression of some starch synthesis-related enzyme genes.…”

Maize endosperm-specific transcription factors O2 and PBF network the regulation of protein and starch synthesis

“…On the other hand, thus far there have been only a few reports regarding transcriptional regulation of starch synthesis in cereals. Among them, one barley WRKY transcription factor, SUSIBA2, and three maize transcription factors, ZmNAC36, ZmbZIP91, and ZmEREB156, are thought to regulate the expression of starch-synthetic genes based on transcriptional activation and/or EMSA assays of their promoters (22)(23)(24)(25). Recently, a study in rice showed that OsbZIP58, the closest homologous protein of maize O2, regulates the expression of multiple genes in the starch biosynthetic pathways, and its null mutants cause abnormal seed morphology with decreased amounts of seed starch (26).…”

NAC-type transcription factors regulate accumulation of starch and protein in maize seeds

“…The previous studies also tried to identify TFs regulating synthetic starch genes by coexpression analysis and biochemistry experiments, like the Electrophoretic Mobility Shift Assay (EMSA) and the Dual-Luciferase Reporter (DLR) assay. There have been candidate TFs, including one barley WRKY transcription factor of SUSIBA2, and three maize transcription factors of ZmNAC36, ZmbZIP91, and ZmEREB156, although their regulatory function on starch synthesis remains to be validated (20)(21)(22)(23).…”