Exogenous application of 5-aminolevulinic acid alleviated damage to wheat chloroplast ultrastructure under drought stress by transcriptionally regulating genes correlated with photosynthesis and chlorophyll biosynthesis

Abstract

5-Aminolevulinic acid (ALA), as a precursor of plant chlorophyll synthesis, can alleviate damage to photosynthesis and thus improve the drought resistance of plants, but the mechanism behind this is still obscure, especially its correlation with functional gene transcription and noncoding RNA regulation. The leaves were collected from Aikang-58 wheat seedlings subjected to drought stress and exogenous ALA application for ultrastructure observation and gene transcription analysis. The results indicated that drought stress attenuated the photosynthesis evidenced by the decrease of net photosynthetic rate (P n ) and stomatal conductance (g s ), damaged the chloroplast ultrastructure by destroying the thylakoid matrix, degrading the chlorophyll, and leading to lipid peroxidation of the cells due to the toxicity of free radicals, causing lipids to dissociate and combine with osmium acid to form plastoglobuli. Under drought stress, exogenous ALA pretreatment can increase the transcript abundance of the chlorophyll synthesis-related genes. Moreover, exogenous ALA increased psb28 transcript abundance under drought stress, to alleviate the damage to the chloroplast ultrastructure and photosynthesis. Our data revealed the possible gene transcriptional regulation patterns in response to drought stress and exogenous ALA alleviation.

Overexpression of the Wheat TaPsb28 Gene Enhances Drought Tolerance in Transgenic Arabidopsis

“…To investigate the response of wheat TaPsb28 gene transcription under drought stress, we exposed seedlings of three wheat cultivars, Zhengmai 1860, Bainong 207, and Zhoumai 18, to 7-day drought stress. As shown in Figure 2 , the transcription of TaPsb28 in the three tested wheat seedlings all decreased significantly by 23%, 49%, and 47%, respectively ( p < 0.05), suggesting that the transcription of psb28 is associated with the resistance of wheat to drought stress study [ 7 ].…”

“…The total chlorophyll content (C t ), chlorophyll a (C a ), and chlorophyll b (C b ) were calculated using the following equations: C a = 13.95A 665 − 6.88A 649 , C b = 24.96A 649 − 7.32A 665 , C t = C a + C b , respectively. The malondialdehyde (MDA) content was determined using 1.0 g Arabidopsis leaves as described previously [ 7 ].…”

“…Transcriptome analysis showed that psb28 gene transcription was induced through circRNA-miRNA-mRNA regulation under drought stress [ 6 ]. Its transcriptional induction by exogenous 5-aminolevulinic acid was also closely related to drought tolerance in different wheat cultivars [ 7 ]. In addition, the protein and/or transcript levels of Psb28 have also been reported to decrease in drought-stressed Nostoc flagelliforme [ 8 ], Panicum miliaceum [ 9 ], and maize [ 10 ].…”

“…In addition, the protein and/or transcript levels of Psb28 have also been reported to decrease in drought-stressed Nostoc flagelliforme [ 8 ], Panicum miliaceum [ 9 ], and maize [ 10 ]. Psb28 was defined as one of the most important stress–responsive genes, because its upregulation was most likely to associate with the alleviation of the damage to plant chloroplast ultrastructure and photosynthesis [ 7 ]. In rice, leaves exhibited a light-green phenotype after the Psb28 gene was inactivated by T-DNA insertion, indicating that it is required for normal growth and pigmentation and that this protein may contribute to stabilizing PSII activity [ 11 ].…”

“…Our previous studies revealed that the wheat TaPsb28 gene was upregulated under drought stress [ 7 ], suggesting that it may be involved in the drought response. In this study, to characterize the role of TaPsb28 in response to drought stress, it was overexpressed in transgenic Arabidopsis and the following physiological and molecular responses to drought stress were analysed.…”