A Phloem Protein Contributes to Aphid Resistance and Heat Stress Tolerance
Author:Kathleen L. Farquharson
Aphids (蚜虫) are highly destructive (破坏性的) insect pests—in addition to robbing plants of sugar-rich phloem sap (韧皮部汁液), they carry viruses that can be deadly to the plant. To reach the phloem sap, aphids must penetrate (穿透) the plasma membrane (质膜) of sieve elements (筛管分子). Mature sieve elements, which are virtually (实际上) empty, translocate (转运) carbohydrates (碳水化合物) and signaling molecules (信号分子), such as RNAs and soluble proteins, but also contain structural proteins of various shapes and sizes. While the functions of most of these proteins are unknown, some protect the plant from sap-sucking insects; a spindle-shaped (梭状的) phloem protein present in legumes (豆科植物) expands when phloem is damaged, forming occlusions (闭塞) that inhibit aphid feeding (Medina-Ortega and Walker, 2015), and a phloem sap lectin (凝集素) in Arabidopsis thaliana limits aphid feeding (Zhang et al., 2011), possibly by interfering with digestion (消化) in the insect’s midgut (中肠) (Kehr,2006).