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The Arabidopsis NFYA5 Transcription Factor Is Regulated Transcriptionally and Posttranscriptionally to Promote Drought Resistance^[W]

^a Key Laboratory of Plant and Soil Interactions, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100094, China
^b Center for Plant Cell Biology, Institute for Integrative Genome Biology and Department of Botany and Plant Sciences, University of California, Riverside, California 92521
^c Department of Plant Science and Landscape Architecture, University of Maryland, College Park, Maryland 20742
^d Department of Horticulture, College of Agriculture, Shihezi University, Xinjiang 832003, China
^e Department of Statistics, Center for Plant Cell Biology and Institute for Integrative Genome Biology, University of California, Riverside, California 92521
^f Department of Plant Pathology, Center for Plant Cell Biology and Institute for Integrative Genome Biology, University of California, Riverside, California 92521

¹ Address correspondence to jian-kang.zhu{at}ucr.edu.

Nuclear factor Y (NF-Y) is a ubiquitous transcription factor composed of three distinct subunits (NF-YA, NF-YB, and NF-YC). We found that the Arabidopsis thaliana NFYA5 transcript is strongly induced by drought stress in an abscisic acid (ABA)-dependent manner. Promoter:β-glucuronidase analyses showed that NFYA5 was highly expressed in vascular tissues and guard cells and that part of the induction by drought was transcriptional. NFYA5 contains a target site for miR169, which targets mRNAs for cleavage or translational repression. We found that miR169 was downregulated by drought stress through an ABA-dependent pathway. Analysis of the expression of miR169 precursors showed that miR169a and miR169c were substantially downregulated by drought stress. Coexpression of miR169 and NFYA5 suggested that miR169a was more efficient than miR169c at repressing the NFYA5 mRNA level. nfya5 knockout plants and plants overexpressing miR169a showed enhanced leaf water loss and were more sensitive to drought stress than wild-type plants. By contrast, transgenic Arabidopsis plants overexpressing NFYA5 displayed reduced leaf water loss and were more resistant to drought stress than the wild type. Microarray analysis indicated that NFYA5 is crucial for the expression of a number of drought stress–responsive genes. Thus, NFYA5 is important for drought resistance, and its induction by drought stress occurs at both the transcriptional and posttranscriptional levels.