Abstract: 【Aim】 α-Galactosidase A (GLA), an enzyme crucial for growth and development, nutrient absorption and stress response of organisms, has been extensively studied in both animals and plants. However, the function of GLA in mites has not been reported. This study aims to explore the role of GLA gene in the feeding process of Tetranychus urticae on its host plants, providing important theoretical insights for the development of novel pest mite control strategies. 【Methods】 Based on the genome and salivary proteome of T. urticae, the full-length open reading frame (ORF) sequence of TuGLA was obtained, and bioinformatic analysis was performed using Expasy, Clustal, Jalview and MEGA. RT-qPCR was used to detect the expression levels of TuGLA at different developmental stages (egg, larva, protonymph, deunymph and female adult) of T. urticae, and in female adults of T. urticae at different feeding time points (1, 3, 6, 9, 12 and 24 h) on kidney bean leaves and at 12 h after feeding on different host plant leaves (kidney bean, tomato, cucumber, corn, cotton and tobacco). RNAi was employed to silence TuGLA by feeding female adults of T. urticae with dsTuGLA, and subsequently the mortality within 5 d and number of eggs laid within 5 d, and the feeding damaged area of kidney bean leaves were calculated. 【Results】 The full-length coding sequence (CDS) of TuGLA (GenBank accession number: XP_015794636.1) of T. urticae is 1 275 bp, encoding 424 amino acids, with a predicted protein molecular weight of 48 kD and a theoretical isoelectric point of 5.01. The 1st-18th amino acids at the N-terminus are signal peptide sequences of TuGLA without transmembrane domains. TuGLA was most closely related to GLAs in Tetranychus genus. TuGLA was expressed in various developmental stages of T. urticae, with the highest expression level in the adult stage. The expression level of TuGLA in female adults of T. urticae at 9 h after feeding on kidney bean leaves was the highest and those in female adults of T. urticae at 12 h after feeding on leaves of tomato, cucumber, corn, cotton and tobacco were significantly up-regulated as compared with those in female adults of T. urticae at 12 h after feeding on kidney bean leaves of the control group. After silencing TuGLA, the mortality within 5 d and the number of eggs laid within 5 d of female adults of T. urticae were significantly increased and reduced, respectively, and the feeding damaged area of kidney bean leaves within 24 h significantly decreased after silencing TuGLA as compared to the those of the dsGFP control group. After silencing TuGLA, the mortality of T. urticae fed on the leaves of kidney bean within 3 d significantly increased as compared with that of the dsGFP control group.【Conclusion】 The feeding on different host plants and feeding duration by T. urticae can induce the expression of TuGLA. Silencing TuGLA by RNAi can significantly affect the survival rate and number of eggs laid of T. urticae, and its damage to host plants. The results of this study provide a theoretical basis for further exploring the feeding mechanism of T. urticae.

Key words: Tetranychus urticae, α-galactosidase A, salivary protein, feeding, RNAi