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

Abstract

Loquat (Eriobotrya japonica 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 EjFAD8 was closely associated with low temperatures. Phenotypic observations and measurements of physiological indicators in Arabidopsis showed that overexpressing-EjFAD8 transgenic plants were significantly more tolerant to low temperatures compared to the wild-type. Heterologous overexpression of EjFAD8 enhanced some lipid metabolism genes in Arabidopsis, 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 FAD8 in loquat under low temperatures lead to desaturation of fatty acids. On the one hand, overexpression of EjFAD8 in Arabidopsis increased the expression of ICE-CBF-COR genes in response to low temperatures. On the other hand, upregulation of EjFAD8 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 EjFAD8 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.

Carbon dioxide treatment modulates phosphatidic acid signaling and stress response to improve chilling tolerance and postharvest quality in paprika

“…This is of particular significance, considering that the balance of unsaturated fatty acids within the lipid bilayer plays a pivotal role in plant responses to CI ( Zhang and Tian, 2010 ). Moreover, heterologous overexpression of Eriobotrya japonica’s FAD8 in Arabidopsis increased the expression of ICE - CBF - cold regulated genes in response to low temperatures ( Xu et al., 2023 ), indicating intricate interaction between lipid process and stress signaling during chilling stress.…”

Polyploidization: A Biological Force That Enhances Stress Resistance

“…Furthermore, omega-3 fatty acid (FA) desaturase, EjFAD8, in triploid loquats (Eriobotrya japonica Lindl. ), localized in the chloroplast, showed significant upregulation under low temperatures and potentially contributed to the enhanced cold resistance by increasing lipid unsaturation levels, including sulfoquinovosyl diacylglycerol (SQDG) and chloroplast content [86]. In addition, BnFLC2 and BnFLC3 are key FLC homologs in B. napus, which play a crucial role in responding to cold stress by regulating the flowering time [87].…”

“…For instance, the EjFAD8 protein boosts the expression of genes associated with low-temperature resistance and participates in the ICE-CBF-COR cold tolerance pathway. Furthermore, EjFAD8 contributes to the stability of photosynthesis in loquats by regulating ROS in chloroplasts, thereby improving stress resistance in triploid loquats [86]. In addition, exposure to ABA or salt triggered the shuttling of NUCLEAR FACTOR Y SUBUNIT C 9 (PtoNF-YC9) into the nucleus, where it interacted with the SALT RESPONSIVE MYB TRANSCRIPTION FACTOR (SRMT, a MYB gene), leading to the rapid expression of RESPONSIVE TO DESICCATION 26 (PtoRD26), which, in turn, directly regulated SRMT.…”