Abstract
BackgroundDigalactosyldiacylglycerol (DGDG) is one of the major lipids found predominantly in the photosynthetic membrane of cyanobacteria, eukaryotic algae and higher plants. DGDG, along with MGDG (Monogalactosyldiacylglycerol), forms the matrix in thylakoid membrane of chloroplast, providing the site for photochemical and electron transport reactions of oxygenic photosynthesis.ResultsIn silico analysis reveals that rice (Oryza sativa L.) genome has 5 genes encoding DGDG synthase, which are differentially expressed in different tissues, and OsDGD2β was identified to be the sole DGDG synthase gene expressed in anther. We then developed osdgd2β mutants by using the CRISPR/Cas9 system and elucidate its role, especially in the development of anther and pollen. The loss of function of OsDGD2β resulted in male sterility in rice characterized by pale yellow and shrunken anther, devoid of starch granules in pollen, and delayed degeneration of tapetal cells. The total fatty acid and DGDG content in the anther was reduced by 18.66% and 22.72% in osdgd2β, affirming the importance of DGDG in the development of anther. The mutants had no notable differences in the vegetative phenotype, as corroborated by relative gene expression of DGDG synthase genes in leaves, chlorophyll measurements, and analysis of photosynthetic parameters, implying the specificity of OsDGD2β in anther.ConclusionOverall, we showed the importance of DGDG in pollen development and loss of function of OsDGD2β results in male sterility. Here, we have also proposed the use of OsDGD2β in hybrid rice breeding using the nuclear male sterility system.
Highlights
Digalactosyldiacylglycerol (DGDG) is one of the major lipids found predominantly in the photosynthetic membrane of cyanobacteria, eukaryotic algae and higher plants
Three genes orthologous to AtDGD1 were designated as OsDGD1α, OsDGD1β and OsDGD1δ, while the two orthologous to AtDGD2 were assigned name as OsDGD2α and OsDGD2β (Additional file 2: Figure S1A)
The gene structures showed that the sequences are not well conserved among the rice DGDG synthase genes
Summary
Digalactosyldiacylglycerol (DGDG) is one of the major lipids found predominantly in the photosynthetic membrane of cyanobacteria, eukaryotic algae and higher plants. The galactolipids in the photosynthetic membranes of higher plants mostly consist of monogalactosyldiacylglycerol (MGDG). DGDG is synthesized from MGDG by transferring a second galactose onto the MGDG by the enzyme DGDG synthase (Ohlrogge and Browse 1995; Mizusawa and Wada 2012). Under the phosphate starvation conditions, AtDGD2 has been reported to be responsible for synthesizing the residual DGDG (Kelly and Dörmann 2002; Jouhet et al 2004), which is exported to various extraplastidial membranes, substituting for phospholipids to maintain cell membrane homeostasis (Hartel et al 2000; Boudière et al 2014)
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