Key Laboratory of Entomology and Pest Control Engineering, College of Plant Protection, Southwest University, Chongqing, China; International Joint Laboratory of China-Belgium on Sustainable Crop Pest Control, Academy of Agricultural Sciences, Southwest University, Chongqing, China.
Key Laboratory of Entomology and Pest Control Engineering, College of Plant Protection, Southwest University, Chongqing, China.
Insect Biochem Mol Biol. 2022 Nov;150:103846. doi: 10.1016/j.ibmb.2022.103846. Epub 2022 Oct 4.
Aphids feed on plant phloem sap that contains massive amounts of sucrose; this not only provides vital nutrition for the aphids but also produces high osmotic pressure. To utilize this carbon source and overcome the osmotic pressure, sucrose is hydrolyzed into the monosaccharides, glucose and fructose. In the green peach aphid (Myzus persicae), we show that this process is facilitated by a key α-glucosidase (MpAgC2-2), which is abundant in the aphid salivary gland and is secreted into leaves during feeding. MpAgC2-2 has a pH optimum of 8.0 in vitro, suggesting it has adapted to the environment of plant cells. Silencing MpAgC2-2 (but not the gut-specific MpAgC3-4) significantly increased the amount of sucrose ingested and hindered aphid feeding on the phloem of tobacco seedlings, resulting in a smaller body size, as well as lower α-glucosidase activity and glucose levels. These effects could be rescued by feeding aphids on tobacco plants transiently expressing MpAgC2-2. The transient expression of MpAgC2-2 also led to the hydrolysis of sucrose in tobacco leaves. Taken together, these results demonstrate that MpAgC2-2 is a salivary protein that facilitates extra-intestinal feeding via sucrose hydrolysis. Our findings provide insight into the ability of aphids to digest the high concentration of sucrose in phloem, and the underlying mechanism of extra-intestinal digestion.
蚜虫以植物韧皮部汁液为食，其中含有大量蔗糖；这不仅为蚜虫提供了重要的营养，还产生了高渗透压。为了利用这个碳源并克服渗透压，蔗糖被水解成单糖，葡萄糖和果糖。在绿桃蚜（Myzus persicae）中，我们表明这个过程是由一种关键的α-葡萄糖苷酶（MpAgC2-2）促进的，该酶在蚜虫的唾液腺中大量存在，并在进食时分泌到叶片中。MpAgC2-2 在体外的最适 pH 值为 8.0，表明它已经适应了植物细胞的环境。沉默 MpAgC2-2（而不是肠道特异性的 MpAgC3-4）显著增加了蚜虫摄入的蔗糖量，并阻碍了蚜虫对烟草幼苗韧皮部的取食，导致体型变小，α-葡萄糖苷酶活性和葡萄糖水平降低。通过在烟草植株上瞬时表达 MpAgC2-2 可以挽救蚜虫的这些影响。MpAgC2-2 的瞬时表达也导致了烟草叶片中蔗糖的水解。综上所述，这些结果表明 MpAgC2-2 是一种唾液蛋白，通过蔗糖水解促进肠外取食。我们的研究结果揭示了蚜虫消化韧皮部中高浓度蔗糖的能力，以及肠外消化的潜在机制。
