Brassica napus miR169 regulates BnaNF-YA in salinity, drought and ABA responses

Abstract

The NF-YA transcription factor in plants is a subunit of the NF-Y (NUCLEAR FACTOR-Y) complex, which plays important roles in plant stress responses and development. The transcripts of genes encoding NF-YA are predicted to be cleaved by members of the miR169 family. We previously identified several miR169s from rapeseed (Brassica napus) based on high-throughput sequencing. In this study, by using 5′ RACE and transient expression in Nicotiana benthamiana, we established that Bna-MIR169m, Bna-MIR169n, Bna-MIR169t (newly identified in this study) cleave target BnaNF-YAs. Quantitative PCR analysis revealed that most Bna-MIR169s detected in the leaves and roots were responsive to salinity, drought, and abscisic acid (ABA) treatment. To examine that these regulations are delivered to downstream of NF-YA, Bna-MI169n and BnaNF-YA9 were heterologously expressed in Arabidopsis thaliana plants. Bna-MI169n exhibited delayed seed germination and root elongation, oppositely, those expressing BnaNF-YA9 had higher rates of seed germination and root elongation under abiotic stress compared to untransformed Arabidopsis. Furthermore, through digital gene expression profiling, we identified several downstream genes co-regulated by Bna-miR169n and BnaNF-YA9. All these results point out that Bna-miR169n and BnaNF-YA9 form a cascade regulates plant abiotic stress responses.