Table_3_The Indole-3-Acetamide-Induced Arabidopsis Transcription Factor MYB74 Decreases Plant Growth and Contributes to the Control of Osmotic Stress Responses.XLSX

The accumulation of the auxin precursor indole-3-acetamide (IAM) in the ami1 mutant has recently been reported to reduce plant growth and to trigger abiotic stress responses in Arabidopsis thaliana. The observed response includes the induction of abscisic acid (ABA) biosynthesis through the promotion of NCED3 expression. The mechanism by which plant growth is limited, however, remained largely unclear. Here, we investigated the transcriptional responses evoked by the exogenous application of IAM using comprehensive RNA-sequencing (RNA-seq) and reverse genetics approaches. The RNA-seq results highlighted the induction of a small number of genes, including the R2R3 MYB transcription factor genes MYB74 and MYB102. The two MYB factors are known to respond to various stress cues and to ABA. Consistent with a role as negative plant growth regulator, conditional MYB74 overexpressor lines showed a considerable growth reduction. RNA-seq analysis of MYB74 mutants indicated an association of MYB74 with responses to osmotic stress, water deprivation, and seed development, which further linked MYB74 with the observed ami1 osmotic stress and seed phenotype. Collectively, our findings point toward a role for MYB74 in plant growth control and in responses to abiotic stress stimuli.

近期有研究报道，ami1突变体中生长素前体吲哚-3-乙酰胺（indole-3-acetamide，IAM）的积累会抑制拟南芥（Arabidopsis thaliana）的生长，并触发其非生物胁迫响应。该响应包含通过促进NCED3基因表达来诱导脱落酸（abscisic acid，ABA）的生物合成。然而，植物生长受抑制的具体分子机制此前仍未明确。本研究通过全面的RNA测序（RNA-sequencing，RNA-seq）与反向遗传学手段，探究了外源施加IAM所诱导的转录响应。RNA测序结果显示，少量基因的表达被诱导，其中包括R2R3型MYB转录因子基因MYB74与MYB102。已知这两种MYB转录因子可响应多种胁迫信号与脱落酸。作为植物生长的负调控因子，MYB74的条件性过表达株系表现出显著的生长抑制。对MYB74突变体的RNA测序分析表明，MYB74与渗透胁迫、水分缺失响应及种子发育过程相关，这进一步将MYB74与此前观察到的ami1突变体渗透胁迫与种子表型关联起来。综上，本研究结果表明MYB74在植物生长调控与非生物胁迫刺激响应中发挥重要作用。