A microRNA switch for nitrogen deficiency | Nature Plants

Nov 08, 2024

Plant nutrition

Nature Plants (2024)Cite this article

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One of the most apparent responses to nitrogen starvation is leaf yellowing due to starvation-induced senescence. Most leaf nitrogen is found in chloroplasts, so degradation of chloroplast components can free up much of these nitrogen reserves to be transported to sink tissues and support root growth, thereby enhancing foraging for new resources. A key transcription factor that regulates nitrogen-starvation-induced senescence is ORESARA1 (ORE1), the transcript of which is targeted and degraded by the microRNA miR164 under nitrogen-replete conditions. Other microRNAs, such as miR169 and miR826, were previously found to regulate the nitrogen deficiency response, but it remains unclear whether and how these individual factors are coordinated.

The researchers performed an expression genome-wide association study (eGWAS) with over fifty Arabidopsis accessions that show variation in the expression of three genes involved in the nitrogen deficiency response. Apart from ORE1, these were the genes encoding the transcription factors NAC-like, activated by AP3/PI (NAP) and Arabidopsis NAC-domain containing protein 55 (ANAC055). The strongest association with the expression of these factors was for mutations in the HST gene. Expression of ORE1, NAP and ANAC055, as well as nitrogen-deficiency-induced leaf yellowing, was anticorrelated with HST protein levels. In line with the reported function of HST in microRNA biogenesis, substantial alterations in microRNA accumulation were shown in hst mutants compared to the wild type under both control and nitrogen-deficient conditions. A T1006A polymorphism in HST accumulates in accessions with high expression of ORE1, NAP and ANAC055, and this polymorphism appears to weaken the interaction between HST and DICER-LIKE1 (DCL1) as well as a range of nitrogen-deficiency-related microRNAs. This is also the case for HST that does not carry the T1006A polymorphism under nitrogen-deficient conditions. Hence, HST might act as a switch that, under nitrogen deficiency, reduces the biogenesis of an entire set of microRNAs, which leads to the accumulation of transcripts involved in the nitrogen deficiency response.

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Raphael Trösch

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Correspondence to Raphael Trösch.

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Trösch, R. A microRNA switch for nitrogen deficiency. Nat. Plants (2024). https://doi.org/10.1038/s41477-024-01861-2

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Published: 05 November 2024

DOI: https://doi.org/10.1038/s41477-024-01861-2

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