Abstract
BackgroundDeveloping Medicago sativa L. (alfalfa) cultivars tolerant to drought is critical for the crop’s sustainable production. miR156 regulates various plant biological functions by silencing SQUAMOSA-PROMOTER BINDING PROTEIN-LIKE (SPL) transcription factors.ResultsTo understand the mechanism of miR156-modulated drought stress tolerance in alfalfa we used genotypes with altered expression levels of miR156, miR156-regulated SPL13, and DIHYDROFLAVONOL-4-REDUCTASE (DFR) regulating WD40–1. Previously we reported the involvement of miR156 in drought tolerance, but the mechanism and downstream genes involved in this process were not fully studied. Here we illustrate the interplay between miR156/SPL13 and WD40–1/DFR to regulate drought stress by coordinating gene expression with metabolite and physiological strategies. Low to moderate levels of miR156 overexpression suppressed SPL13 and increased WD40–1 to fine-tune DFR expression for enhanced anthocyanin biosynthesis. This, in combination with other accumulated stress mitigating metabolites and physiological responses, improved drought tolerance. We also demonstrated that SPL13 binds in vivo to the DFR promoter to regulate its expression.ConclusionsTaken together, our results reveal that moderate relative miR156 transcript levels are sufficient to enhance drought resilience in alfalfa by silencing SPL13 and increasing WD40–1 expression, whereas higher miR156 overexpression results in drought susceptibility.
Highlights
Developing Medicago sativa L. cultivars tolerant to drought is critical for the crop’s sustainable production. miR156 regulates various plant biological functions by silencing SQUAMOSA-PROMOTER BINDING PROTEINLIKE (SPL) transcription factors
SPL13 acts as a transcriptional suppressor of DFR during drought stress as confirmed by higher expression of DFR in SPL13RNAi and miR156OE plants
We recently reported that miR156 regulates drought tolerance in alfalfa by silencing SPL13 [21]
Summary
Developing Medicago sativa L. (alfalfa) cultivars tolerant to drought is critical for the crop’s sustainable production. miR156 regulates various plant biological functions by silencing SQUAMOSA-PROMOTER BINDING PROTEINLIKE (SPL) transcription factors. MiR156 regulates various plant biological functions by silencing SQUAMOSA-PROMOTER BINDING PROTEINLIKE (SPL) transcription factors. The effects of climate change are expected to result in frequent and extreme weather events causing major damage to crop production [1, 2]. Plants respond to these changes (abiotic stress) by developing different resilience mechanisms at the phenotypic, physiological and molecular levels [3]. (miR156) is highly conserved in plants, where it functions by down-regulating a group of SQUAMOSAPROMOTER BINDING PROTEIN-LIKE (SPL) transcription factors [7,8,9].
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