Glycerophosphodiester phosphodiesterase 1 mediates G3P accumulation for Eureka lemon resistance to citrus yellow vein clearing virus

Glycerophosphodiester phosphodiesterase 1 (GDPD1) plays an important function in the abiotic stress responses and participates in the accumulation of sn-glycerol-3-phosphate (G3P) in plants, which is key to plant systemic acquired resistance (SAR). However, the role of GDPD1 in plant responses to biotic stress remains poorly understood. This study characterized the antivirus function of the GDPD1 gene (designated as ClGDPD1) from Eureka lemon. ClGDPD1 is located in the membrane and endoplasmic reticulum, where it interacts with the citrus yellow vein clearing virus (CYVCV) coat protein (CP). Compared to individually express ClGDPD1 or co-expressed ClGDPD1 + CP140-326, transiently co-expressed ClGDPD1 + CP or ClGDPD1 + CP1-139 significantly up-regulated the key substance contents and genes expression involved in glycerophospholipid metabolism. Over-expression of ClGDPD1 significantly facilitated the accumulation of G3P, up-regulated the expression of SAR-related genes, and increased the resistance of transgenic Eureka lemon to CYVCV infection. Furthermore, exogenous glycerol treatment and over-expression of ClGPDH increased the G3P content and reduced CYVCV titers in plants or hairy roots. These results indicated that the enhanced resistance of ClGDPD1 transgenic Eureka lemon to CYVCV may be due to facilitating G3P accumulation through the interaction of ClGDPD1 with CP. Our findings provide novel insights into the role of ClGDPD1 as an important regulatory center in mediating the citrus defense response to viral infections.