Abstract
Alfin-like (AL) is a small plant-specific gene family with prominent roles in root growth and abiotic stress response. Here, we aimed to identify novel stress tolerance AL genes from the stress-tolerant species Atriplex hortensis. Totally, we isolated four AhAL genes, all encoding nuclear-localized proteins with cis-element-binding and transrepression activities. Constitutive expression of AhAL1 in Arabidopsis facilitated plants to survive under saline condition, while expressing anyone of the other three AhAL genes led to salt-hypersensitive response, indicating functional divergence of AhAL family. AhAL1 also conferred enhanced drought tolerance, as judged from enhanced survival, improved growth, decreased malonaldehyde (MDA) content and reduced water loss in AhAL1-expressing plants compared to WT. In addition, abscisic acid (ABA)-mediated stomatal closure and inhibition of seed germination and primary root elongation were enhanced in AhAL1-transgenic plants. Further analysis demonstrated that AhAL1 could bind to promoter regions of GRF7, DREB1C and several group-A PP2C genes and repress their expression. Correspondingly, the expression levels of positive stress regulator genes DREB1A, DREB2A and three ABFs were all increased in AhAL1-expressing plants. Based on these results, AhAL1 was identified as a novel candidate gene for improving abiotic stress tolerance of crop plants.
Highlights
Plant adaptation to long-term environmental stress requires integrated changes in regulation of functional genes for physiological adjustments in both cellular and organismal level
A dehydration-responsive element-binding (DREB)-like transcription factor gene was isolated from A. hortensis and could promote stress tolerance when expressed in tobacco plants[32]
Four full-length Alfin-like genes were isolated from halophyte A. hortensis using degenerate RT-PCR and RACE methods
Summary
Plant adaptation to long-term environmental stress requires integrated changes in regulation of functional genes for physiological adjustments in both cellular and organismal level. Expressing GmPHD2, an Alfin-like gene from soybean, promoted the salt tolerance of transgenic Arabidopsis plants, probably by eliminating the excessive stress-induced Reactive Oxygen Species (ROS)[21]. Another Alfin-like protein GmPHD5 from soybean seems to be an important regulator of the histone methylation-acetylation crosstalk in response to salt stress. AL5 from Arabidopsis could bind directly to promoters of various downstream genes and inhibit expression of these negative regulators for plant adaptation to salt, drought and freezing stress[14] These findings suggest that AL family proteins play important roles in regulating plant responses to environmental stimuli. Our study reveals functional divergence of different AL members in abiotic stress response and identified AhAL1 as a potential candidate gene for enhancing stress tolerance of crop plants
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