CIPK15-mediated inhibition of NH4+transport protects Arabidopsis from submergence
Nitrogen is widely recognized as a crucial element for plants due to its role as a fundamental building block for essential macromolecules such as nucleic acids, amino acids, and proteins. In most soils, nitrogen primarily exists in inorganic forms, including nitrate (NO3−) and ammonium (NH4+). Numerous studies have confirmed that the nitrogen content in soil significantly influences plant growth and development.
However, when plants are exposed to hypoxic flooding conditions, the conversion of nitrate (NO3−) into ammonium (NH4+) through the process of nitrification is inhibited, leading to the accumulation of NH4+ in the soil. Previous research has established that an excessive accumulation of ammonium can be toxic to plants. On the other hand, under hypoxic conditions, it is known that the CBL-interacting protein kinase OsCIPK15 can initiate the SnRK1A signaling pathway, promoting starch mobilization and thereby increasing the availability of ATP, reducing agents, and facilitating NH4+ assimilation.
Building upon our team's prior investigations, we have uncovered the role of AtCIPK15 in Arabidopsis, where it phosphorylates the AMT1;1 protein, concurrently regulating NH4+ uptake into plant roots. In further studies, we observed that submergence leads to the accumulation of NH4+ in wild-type Arabidopsis plants but not nitrate (NO3−). Furthermore, this phenomenon was not observed in quadruple amt gene knockout mutants. Moreover, flooding rapidly induces the transcription of both AtAMT1;1 and AtCIPK15, along with the phosphorylation of the AMT1 protein. Notably, cipk15 gene knockout mutants do not exhibit an increase in AMT1 phosphorylation but display heightened sensitivity during flooding conditions.
In summary, our findings reveal that Arabidopsis can mitigate ammonium toxicity in hypoxic environments, such as flooding, through the inhibition of AMT activity mediated by CIPK15.
Yen-Ning Chen and Cheng-Hsun Ho* (2023) CIPK15-mediated inhibition of NH4+transport protects Arabidopsis from submergence HELIYON, Volume 9, Issue 9, e20235, ISSN 2405-8440, https://doi.org/10.1016/j.heliyon.2023.e20235