The Jasmonate-ZIM Domain Proteins Interact with the R2R3-MYB Transcription Factors MYB21 and MYB24 to Affect Jasmonate-Regulated Stamen Development in Arabidopsis    

Abstract

The Arabidopsis thaliana F-box protein CORONATINE INSENSITIVE1 (COI1) perceives jasmonate (JA) signals and subsequently targets the Jasmonate-ZIM domain proteins (JAZs) for degradation by the SCF COI1 -26S proteasome pathway to mediate various jasmonate-regulated processes, including fertility, root growth, anthocyanin accumulation, senescence, and defense. In this study, we screened JAZ-interacting proteins from an Arabidopsis cDNA library in the yeast two-hybrid system. MYB21 and MYB24, two R2R3-MYB transcription factors, were found to interact with JAZ1, JAZ8, and JAZ11 in yeast and in planta. Genetic and physiological experiments showed that the myb21 myb24 double mutant exhibited defects specifically in pollen maturation, anther dehiscence, and filament elongation leading to male sterility. Transgenic expression of MYB21 in the coi1-1 mutant was able to rescue male fertility partially but unable to recover JA-regulated root growth inhibition, anthocyanin accumulation, and plant defense. These results demonstrate that the R2R3-MYB transcription factors MYB21 and MYB24 function as direct targets of JAZs to regulate male fertility specifically. We speculate that JAZs interact with MYB21 and MYB24 to attenuate their transcriptional function; upon perception of JA signal, COI1 recruits JAZs to the SCF COI1 complex for ubiquitination and degradation through the 26S proteasome; MYB21 and MYB24 are then released to activate expression of various genes essential for JA-regulated anther development and filament elongation.

A bHLH-Type Transcription Factor, ABA-INDUCIBLE BHLH-TYPE TRANSCRIPTION FACTOR/JA-ASSOCIATED MYC2-LIKE1, Acts as a Repressor to Negatively Regulate Jasmonate Signaling inArabidopsis

“…However, new insights have recently emerged on the regulatory mechanisms of JA signaling, including identification of JAZ binding partners, and the influence of circadian rhythms and hormonal crosstalk (Hou et al, 2010;Qi et al, 2011;Song et al, 2011;Goodspeed et al, 2012;Hong et al, 2012;Shin et al, 2012;Yang et al, 2012). These suggest that JA signaling encompasses multiple complicated regulatory mechanisms.…”

MYB transcription factor genes as regulators for plant responses: an overview

“…Expression analysis of the six TaMYB genes indicated that they were expressed in root, sheath and leaf, but at different abundance. Another study by Song et al (2011) demonstrated that the R2R3-MYB transcription factors MYB21 and MYB24 function as direct targets of JAZs to regulate male fertility specifically. They speculated that JAZs interact with MYB21 and MYB24 to attenuate their transcriptional function; upon perception of JA signal, COI1 recruits JAZs to the SCF COI1 complex for ubiquitination and degradation through the 26S proteasome.…”

Transcriptional Mechanism of Jasmonate Receptor COI1-Mediated Delay of Flowering Time in Arabidopsis

“…These MYC TFs interact with most of the 12 JAZ proteins and act redundantly to regulate diverse aspects of JA responses, including root growth inhibition and defense gene expression Fernández-Calvo et al, 2011;Kazan and Manners, 2013;Schweizer et al, 2013). In addition to these MYC proteins, recent studies have identified numerous TFs that interact with JAZ proteins and regulate different aspects of JAdependent transcriptional responses Song et al, 2011;Zhu et al, 2011;Hu et al, 2013;Jiang et al, 2014).…”