miRNAs are a class of endogenous non-coding small RNAs that regulate gene expression post-transcriptionally. Nitrogen (N) is a key component of many fundamental biological molecules,such as nucleic acids, amino acids, proteins 170 and N-containing metabolites. Thus, plants must obtain sufficient N for normal growth and development. Although many N-starvation responsive miRNAs have been identified, the functions for most of them are unclear under N starvation conditions.

   Prof. Yu Diqiu and his team of Xishuangbanna Tropical Botanical Garden (XTBG) have been studying the functions of miRNAs in Arabidopsis thaliana for a few years. Their previous research showed that many plant miRNAs were responsive to N starvation, among which miR826 was dramatically induced by N starvation.In a recent study, they identified a novel miRNA gene (MIR5090) from the complementary transcript of MIR826.

   To further understand the functions of miR826 and miR5090, they generated transgenic plants overexpressing miR826 or miR5090. The overproduction of miR826 or miR5090 correlated well with the decreased AOP2 mRNA level in transgenic plants, suggesting that miR826 and miR5090 suppressed AOP2 mRNA abundance. Elevated miR826 or miR5090 expression suppressed the function of AOP2, resulting in the reduction of methionine-derived glucosinolates. Both N starvation and AOP2 reduction caused downregulation of glucosinolate synthesis associated genes. miRNA transgenic plants displayed enhanced 408 tolerance to N starvation.

   To analyze whether the tolerance conferred by the two miRNAs in transgenic plants resulted from variation in N acquisition, they determined the N content of transgenic and wild-types. The results suggested that N uptake system in transgenic plants may be improved, leading to enhanced tolerance to N limitation.

Their study revealed that both miR826 and miR5090 regulated A. thaliana’s adaptation to low N conditions by affecting glucosinolate synthesis.

  The study entitled “Two young miRNAs originating from target duplication mediate nitrogen starvation adaptation via regulation of glucosinolate synthesis in Arabidopsis thaliana” has been published online in Plant Physiology.