SSH reveals a linkage between a senescence-associated protease and Verticillium wilt symptom development in lettuce (Lactuca sativa)

Suppression subtractive hybridization (SSH) was employed to identify lettuce (Lactuca sativa) genes that are differentially expressed in symptomatic leaves infected with Verticillium dahliae. Genes expressed only in symptomatic leaves included those with homology to pathogenesis-related (PR) protein genes PR-3, PR-5, and a putative cysteine protease (LsCP2). Quantitative real-time reverse transcription PCR (RT-qPCR) revealed that LsCP2 was expressed in senescent leaves, but at significantly higher levels in symptomatic leaves. LsCP2 shares homology with plant cysteine proteases that are expressed in senescing leaves and may therefore accelerate or contribute to the leaf symptoms observed in a lettuce–V. dahliae interaction.

► Gene expression was analyzed in lettuce infected with Verticillium dahliae. ► Suppression subtractive hybridization (SSH) libraries were prepared. ► Expression of defense-related genes confirmed by RT-qPCR. ► Cysteine protease-encoding gene LsCp2 expressed in senescent and infected leaves. ► LsCp2 expression correlates with leaf symptoms.