Abstract
The Arabidopsis histone deacetylase 6 (HDA6) mutant exhibits increased tolerance to drought stress by negatively regulating the expression of ALDH2B7 and PDC1. Therefore, it was logical to determine if transgenic Arabidopsis plants expressing PDC1 or ALDH2B7 using a suitable promoter would also exhibit tolerance to drought stress. An analysis of published microarray data indicated the up-regulation of the TSPO gene, which encodes an outer membrane tryptophan-rich sensory protein (TSPO), by drought stress. RT-qPCR, as well as GUS analysis of the promoter, confirmed the up-regulation of TSPO by drought stress in Arabidopsis roots and shoots. Thus, the TSPO promoter was used to drive drought-responsive expression of ALDH2B7 and PDC1. RT-qPCR analysis confirmed that the expression of PDC1 and ALDH2B7 was up-regulated, relative to WT plants, by drought stress in homozygous pTSPO-PDC1 and pTSPO-ALDH2B7 plant lines. pTSPO-ALDH2B7 and pTSPO-PDC1 transgenic lines showed prolonged survival under drought stress. Microarray analyses revealed transcriptomic changes related to metabolism in pTSPO-PDC1 plants, indicating that selective regulation of metabolism may occur; resulting in the acquisition of drought stress tolerance. These results confirmed that TSPO promoter can be used to elevate the expression of acetic acid biosynthesis pathway genes; ensuring prolonged survival under drought stress in Arabidopsis.
Highlights
Drought stress negatively impacts photosynthesis and plant growth and can result in reduced crop yield and enormous economic losses
The expression of ALDH2B7 is up-regulated in response to ABA application and dehydration; suggesting that aldehyde dehydrogenase (ALDH) may play a role in aerobic detoxification of acetaldehyde
The resulting transgenic plants exhibited a significant increase in drought stress tolerance. These results demonstrate that the elevated expression of acetic acid biosynthesis pathway genes using a tryptophan-rich sensory protein (TSPO) promoter can significantly enhance drought stress tolerance in Arabidopsis plants
Summary
Drought stress negatively impacts photosynthesis and plant growth and can result in reduced crop yield and enormous economic losses. Acetyl-CoA can be synthesized by an alternative pathway in which PDH is bypassed In this case, PDC proteins convert pyruvate to acetaldehyde, which is subsequently converted to acetate by ALDH enzymes[7,8]. Arabidopsis PDC proteins have been reported to play a role in ethanol fermentation[9,10] Their role in acetate production through a PDH independent pathway, has never been verified or comprehensively discussed. Microarray analyses have indicated that the expression of PDC1 and ALDH2B7 are up-regulated by drought stress These data, combined with the drought tolerant phenotype exhibited by the hda[6] mutant and the enhanced drought tolerance that is induced by the exogenous application of acetic acid[5], strongly suggest that plants expressing PDC1 or ALDH2B7 under the control of a suitable promoter could significantly enhance drought stress tolerance
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