提出问题：Some of these salivary proteins elicit plant defenses, but the molecular and biochemical mechanisms that underlie the activation of phloem-localized resistance remain poorly understood.

研究对象：The aphid Myzus persicae, which is a generalized phloem-sucking pest, encompasses a number of lineages that are associated with and adapted to specific host plant species.

结果1-CathB3蛋白：The current study found that a cysteine protease Cathepsin B3 (CathB3), and the associated gene CathB3, was upregulated in the salivary glands and saliva of aphids from a non-tobacco-adapted (NTA) aphid lineage, when compared to those of a tobacco-adapted lineage.

结果2-功能验证：Furthermore, the knockdown of CathB3 improved the performance of NTA lineages on tobacco, and the propeptide domain of CathB3 was found to bind to tobacco cytoplasmic kinase ENHANCED DISEASE RESISTANCE 1-like (EDR1-like), which triggers the accumulation of reactive oxygen species in tobacco phloem, thereby suppressing both phloem feeding and colonization by NTA lineages.

结论：These findings reveal a novel function for a cathepsin-type protease in aphid saliva that elicits effective host plant defenses and warranted the theory of host specialization for generalist aphids.

 摘  要 

最近的研究报道，蚜虫在刚开始刺吸和取食时，会将唾液蛋白分泌到宿主组织中，促进其在宿主植物中的定殖。这些唾液蛋白中的某些蛋白会诱导植物的防御，但是，目前我们对于韧皮部抗性激活的分子和生化机制仍然知之甚少。桃蚜（Myzus persicae）是一种通常吸食韧皮部的害虫，包含许多适应特定寄主植物的谱系。当前的研究发现，与适应烟草的蚜虫相比，半胱氨酸蛋白酶CathB3和相关基因CathB3在非烟草适应性蚜虫谱系的唾液腺和唾液中上调。此外，CathB3基因的敲低能够增强非烟草适应性蚜虫在在烟草上的表现，并且发现CathB3的前导肽结构域能够与烟草胞质激酶EDR1-like结合，从而诱导了烟草韧皮部活性氧的积累，因而抑制了非烟草适应性蚜虫对于烟草的取食和定殖。这些发现揭示了在蚜虫唾液中cathepsin蛋白酶具有诱导宿主植物有效防御的新功能，并为普通蚜虫的宿主专化提供了理论基础。