Recently, Chinese researchers have found that a short-term low-concentration effect of abscisic acid on rice seedling is synergized, rather than antagonized, through the brassinosteroid (BR) signaling pathway, which sheds new light on current understanding about the interaction between a stress hormone and a growth hormone. This study was published in
Nature Plants on July 5.
The survival of plant depends on the complex interaction of distinct hormone signals in order to maintain an adaptive balance between growth/development and stress tolerance. ABA and BR are two important phytohormones. As the former is one of the most important stress hormone and the latter is a growth-promoting hormone, the complex antagonistic relationship between ABA and BRs has been observed for a long time and studied widely.
Based on a series of physiological and genetic analyses, the researchers led by Prof. CHU Chengcai and Associate Prof. TANG Jiuyou at the Institute of Genetics and Developmental Biology of the Chinese Academy of Sciences disclosed that low concentration ABA activates BR signaling in a fast and short-term manner, resulting in increased lamina joint inclination of rice seedlings.
This finding is consistent with the response of rice seedlings to low concentration of ABA and brassinolide (BL) at the transcriptional level. That is, about 60% of low-concentration ABA early response genes can be regulated by BL in the same directions, while only 1% of them can be regulated by BL in the opposite directions.
Further results revealed that ABA activated BR response partially through induction of BR-biosynthesis regulatory gene OsGSR1, whose expression is directly regulated by transcriptional factor ABI3 but not ABI5.
By testing the potential role of BR short-term activation in ABA-mediated salt tolerance, the researchers suggested that the transient synergism between ABA and BR is not simply used to regulate visible morphological phenotype but also has a biological significance in regulating mild stress tolerance. However, upon severe stress, the effects of ABA-BR synergism are difficult to be detected, while the antagonistic effect of ABA on BR was activated rapidly.
This study therefore reveals the existence of adaptive mechanisms in plant to cope with varying degrees of stress.
This work was supported by the National Natural Science Foundation of China.
