Relationships of brassinosteroid signaling with knox and wab1 genes on maize plant architecture

Abstract

<p>Improving yield through plant architecture manipulation might be an answer to resolve food and fuel problems. Brassinosteroid (BR) is a plant steroid hormone involved in plant architecture. However, the BR pathway is not well known in maize. In this study, we are interested to analyze the relationship among BR, knox, and wab1 in maize. knotted1-like homeobox (knox) genes encode homedomain-containing transcription factors that play roles in regulating BR and plant architecture. wavy auricle in blade1 (wab1) encodes a TCP transcription factor (teosinte branched1, cycloidea, and PCF) that controls leaf architecture. In Arabidopsis, TCP1 also regulates BR. Phenotype and gene expression was analyzed for single and double mutants among maize brassinosteroid insensitive2 (bin2)-RNAi, zea mays brassinosteroid insensitive1 (zmbri1)-RNAi, Knotted1-O (Kn1-O), and Wab1-R lines. Phenotype and gene expression analysis by using qRT-PCR showed suppressed Kn1-O phenotype in Kn1-O/+; bin2-RNAi/+, while enhanced in Kn1-O/+; zmbri1-RNAi, indicating BR signaling suppression to kn1. However, the mechanism was still unclear because there were no significant results from BR genes expression analysis. Similarly, phenotype and gene expression analysis showed suppressed Wab1-R phenotype in Wab1-R/+; bin2-RNAi/+, while enhanced in Wab1-R/+; zmbri1-RNAi, indicating BR signaling suppression to wab1. Interestingly, internode phenotype and brassinosteroid dependent1 (brd1) gene expression analysis also indicate wab1 might regulate BR through brd1, which is similar to BR regulation by TCP1 in Arabidopsis through DWARF4 (DWF4). Gene expression analysis of knox genes and BR catabolism genes showed no significant results. In summary, BR signaling might inhibit kn1, however the mechanism is still unclear and other gene might play a role on the phenotype. BR signaling might inhibit wab1. While, wab1 might also regulate BR through brd1. kn1 and wab1 might not be directly related. wab1 and BR catabolism genes also might not be directly related.</p>