Abstract
BackgroundFreezing stress inhibits plant development and causes significant damage to plants. Plants therefore have evolved a large amount of sophisticated mechanisms to counteract freezing stress by adjusting their growth and development correspondingly. Plant ontogenetic defense against drought, high salt, and heat stresses, has been extensively studied. However, whether the freezing tolerance is associated with ontogenetic development and how the freezing signals are delivered remain unclear.ResultsIn this study, we found that the freezing tolerance was increased with plant age at the vegetative stage. The expressions of microRNA156 (miR156) and SQUAMOSA PROMOTER BINDING PROTEIN-LIKE 9 (SPL9), playing roles in regulation of ontogenetic development, were induced by cold stress. Overexpression of SPL9 (rSPL9) promoted the expression of C-REPEAT BINDING FACTOR 2 (CBF2) and hereafter enhanced the freezing tolerance. Genetic analysis indicated that the effect of rSPL9 on freezing tolerance is partially restored by cbf2 mutant. Further analysis confirmed that SPL9 directly binds to the promoter of CBF2 to activate the expression of CBF2, and thereafter increased the freezing tolerance.ConclusionsTherefore, our study uncovers a new role of SPL9 in fine-tuning CBF2 expression and thus mediating freezing tolerance in plants, and implies a role of miR156-SPL pathway in balancing the vegetative development and freezing response in Arabidopsis.
Highlights
Freezing stress inhibits plant development and causes significant damage to plants
Key message SQUAMOSA PROMOTER BINDING PROTEIN-LIKE 9 (SPL9) directly binds to the promoter of C-REPEAT BINDING FACTOR 2 (CBF2) and activate CBF2 expression to balance the freezing tolerance and plant development
We provide evidence that the capacity of freezing tolerance in plants is increased with plants age; and SPL9 directly binds to the promoters of CBF2 to promote CBF2 expression for enhancing freezing tolerance
Summary
Plants have evolved a large amount of sophisticated mechanisms to counteract freezing stress by adjusting their growth and development correspondingly. Plant ontogenetic defense against drought, high salt, and heat stresses, has been extensively studied. Whether the freezing tolerance is associated with ontogenetic development and how the freezing signals are delivered remain unclear. Overexpression of miR156 increases the juvenile stage with the elevated anthocyanin production in Arabidopsis and rice, and enhances abiotic stress tolerance by regulating the SPL9 and DIHYDROFLAVONOL-4-REDUCTASE (DFR) expressions [6]. Previous study shows that overexpression of miR156 in rice reduces the cold tolerance by repressing the expression of OsSPL14 (or called IDEAL PLANT ARCHITECTURE1 (IPA1)) [7]. The precise molecular mechanism of how miR156-SPLs pathway in an age-dependent manner modulates plant response to cold stress remains elusive
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