Brassinosteroids suppress ethylene-induced fruitlet abscission through LcBZR1/2-mediated transcriptional repression of LcACS1 / 4 and LcACO2 / 3 in litchi

作者：Xingshuai Ma, Ye Yuan, Caiqin Li, Qian Wu, Zidi He, Jianguo Li, Minglei Zhao · 发表于：Horticulture Research · 年份：2021 · DOI：10.1038/s41438-021-00540-z · 被引用次数：50 · 研究领域：Plant Molecular Biology Research、Plant Physiology and Cultivation Studies、Postharvest Quality and Shelf Life Management

Abscission in plants is tightly controlled by multiple phytohormones and the expression of various genes. However, whether the plant hormone brassinosteroids (BRs) are involved in this process is largely unknown. Here, we found that exogenous application of BRs reduced the ethylene-induced fruitlet abscission of litchi due to lower ethylene (ET) production and suppressed the expression of the ethylene biosynthetic genes LcACS1/4 and LcACO2/3 in the fruitlet abscission zone (FAZ). Two genes that encode the BR core signaling components brassinazole resistant (BZR) proteins, namely, LcBZR1 and LcBZR2, were characterized. LcBZR1/2 were localized to the nucleus and acted as transcription repressors. Interestingly, the LcBZR1/2 transcript levels were not changed during ET-induced fruitlet abscission, while their expression levels were significantly increased after BR application. Moreover, gel shift and transient expression assays indicated that LcBZR1/2 could suppress the transcription of LcACS1/4 and LcACO2/3 by specifically binding to their promoters. Importantly, ectopic expression of LcBZR1/2 in Arabidopsis significantly delayed floral organ abscission and suppressed ethylene biosynthesis. Collectively, our results suggest that BRs suppress ET-induced fruitlet abscission through LcBZR1/2-controlled expression of genes related to ethylene biosynthesis in litchi. In addition, similar results were observed in the Arabidopsis gain-of-function mutant bzr1-1D, which showed delayed f...