EjFAD8 Enhances the Low-Temperature Tolerance of Loquat by Desaturation of Sulfoquinovosyl Diacylglycerol (SQDG)

Loquat ( Lindl.) is an evergreen fruit tree of Chinese origin, and its autumn-winter flowering and fruiting growth habit means that its fruit development is susceptible to low-temperature stress. In a previous study, the triploid loquat (B431 × GZ23) has been identified with high photosynthetic efficiency and strong resistance under low-temperature stress. Analysis of transcriptomic and lipidomic data revealed that the fatty acid desaturase gene was closely associated with low temperatures. Phenotypic observations and measurements of physiological indicators in showed that overexpressing- transgenic plants were significantly more tolerant to low temperatures compared to the wild-type. Heterologous overexpression of enhanced some lipid metabolism genes in , and the unsaturation of lipids was increased, especially for SQDG (16:0/18:1; 16:0/18:3), thereby improving the cold tolerance of transgenic lines. The expression of ICE-CBF-COR genes were further analyzed so that the relationship between fatty acid desaturase and the ICE-CBF-COR pathway can be clarified. These results revealed the important role of EjFAD8 under low-temperature stress in triploid loquat, the increase expression of in loquat under low temperatures lead to desaturation of fatty acids. On the one hand, overexpression of in increased the expression of ICE-CBF-COR genes in response to low temperatures. On the other hand, upregulation of at low temperatures increased fatty acid desaturation of SQDG to maintain the stability of photosynthesis under low temperatures. This study not only indicates that the gene plays an important role in loquat under low temperatures, but also provides a theoretical basis for future molecular breeding of loquat for cold resistance.