Exogenous application of 5-aminolevulinic acid on wheat seedlings under drought stress enhances the transcription of psbA and psbD genes and improves photosynthesis
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The compound 5-aminolevulinic acid (ALA) is an essential precursor for the biosynthesis of porphyrins, including chlorophyll, heme, and cytochromes. The protective effects of ALA on photosynthesis and the expression of photosynthetic genes in wheat under drought stress are not well understood. Two wheat cultivars, drought-tolerant Aikang-58 and drought-sensitive Chinese Spring, were exposed to drought stress induced by 20% polyethylene glycol (PEG-6000) after foliar pretreatment with ALA for 3 days. The results showed that exogenous application of ALA protected the drought-stressed wheat seedlings by significantly inhibiting the decrease in relative water and chlorophyll contents. The ALA-mediated alleviation of stress was similar between the drought-tolerant and drought-sensitive wheat cultivars. Meanwhile, compared to seedlings under drought treatment alone, the ALA-pre-treated wheat seedlings under drought stress maintained higher photosystem II (PSII) functional indexes. The ALA pretreatment reduced the drought-driven accumulation of both H2O2 and ABA and increased the stomatal conductance. Real-time PCR analysis showed that the psbA and psbD gene transcripts were both upregulated under drought stress following ALA pretreatment. The present study suggests that the exogenous foliar application of ALA alleviates the drought stress on wheat seedlings, which is associated with the enhancement of PSII function by inducing chlorophyll synthesis and psbA and psbD transcription. Moreover, the protective effect of ALA pretreatment was not related to the decline in stomatal conductance caused by ABA or H2O2 accumulation.
KeywordsCrop plant Exogenous regulation Gene expression Photosystem II Water deficit
One-way analysis of variance
Enzyme-linked immunosorbent assay
Maximum efficiency of PSII photochemistry
Photosynthetic photon flux density
Net photosynthetic rate
Actual quantum yield
Non-photochemical quenching coefficient
Photochemical quenching coefficient
Relative water contents
This study was financially supported by the National Natural Science Foundation of China (Grant No. U1704103), the Education Department of Henan Province (Grant No. 16A210030), the Sci-tech Innovation Foundation of Henan Agricultural University (Grant No. KJCX2016A06), and the National Innovation and Entrepreneurship Training Program of Undergraduate Student in Henan University (201710466013).
YW and HZ contributed to the experimental design and writing of this manuscript. YW, SW, XS, and JW contributed on the performance of experiments. BS and FQ contributed to the data analysis.
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