Yi Keke's research group, from the Innovation Team of Soil-Plant Interactions of the Institute of Agricultural Resources and Regional Planning (IARRP) of the Chinese Academy of Agricultural Sciences (CAAS), has revealed the mechanism of salicylic acid synthesis regulating rice salt tolerance and drought resistance, which has laid the foundation for further research on the role of salicylic acid in crop adaptation to soil adversity stress. The topic was published in "New Phytologist" under the title "AIM1-dependent high basal salicylic acid accumulation modulates stomatal aperture in rice".

Salicylic acid is an important plant hormone that regulates plant growth and development and is widely involved in various stress responses. Salicylic acid is mainly synthesized in plants through two pathways: isochorismate synthase (ICS) and phenylalanine ammonia lyase (PAL). The model plant Arabidopsis thaliana contains lower basal levels of salicylic acid, and stress-induced salicylic acid is synthesized through the ICS pathway. Rice contains higher basal levels of salicylic acid, and the content of salicylic acid in its shoots is almost 100 times that of Arabidopsis. However, the mechanism of high basal salicylic acid in rice is still unclear. The previous study found that the OsAIM1-dependent PAL pathway is involved in the synthesis of salicylic acid in rice roots. The content of salicylic acid in rice shoots is much higher than that in the roots, but how shoots produce high basal levels of salicylic acid and their biological functions is still poorly understood.

In this study, combining metabolite analysis, physiological and genetic methods, it was found that the content of salicylic acid in the shoot of the OsAIM1 gene loss-of-function mutant was much lower than that of the wild type, resulting in a significantly lower temperature in the shoot of rice than in the wild type. The phenotype of the mutant with reduced shoot temperature was due to the increased stomatal opening and enhanced transpiration. Further research found that the stomatal opening of OsAIM1 and OsWRKY45 loss-of-function mutants increased, the level of reactive oxygen species in stomatal guard cells decreased, and the exogenous addition of H2O2 could restore the defects of the mutants. Exogenous salicylic acid treatment could restore the defects in the stomatal opening and reactive oxygen species (ROS) accumulation in OsAIM1 loss-of-function mutant, but not in OsWRKY45 loss-of-function mutant. It was shown that salicylic acid regulates the stomatal opening through the OsWRKY45-ROS pathway. In addition, this regulatory pathway plays an important role in rice adaptation to soil salinity and drought stress.

Salicylic acid regulates the stomatal opening and adversity stress tolerance through the OsWRKY45-ROS pathway [Photo/IARRP]

Xu Lei, associate researcher of the IARRP, postdoctoral fellow Zhao Hongyu, and associate professor Wang Junbin of Tianjin Agricultural College are the co-first authors of the paper. Researcher Yi Keke of the IARRP, Professor Xie Xiaodong of Tianjin Agricultural College and Professor Luo Jie of the Sanya Nanfan Research Institute of Hainan University and Hainan Yazhou Bay Seed Laboratory are the co-corresponding authors.

The research was supported by the Youth Innovation Program of the Chinese Academy of Agricultural Sciences, the National Natural Science Foundation of China, the Natural Science Foundation of Tianjin, and the agricultural Science and Technology Innovation Program of Chinese Academy of Agricultural Sciences.

Paper link: https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.18842