SGT1 positively regulates the process of plant cell death during both compatible and incompatible plant–pathogen interactions

Abstract

SGT1 (suppressor of G2 allele of Skp1), an interactor of SCF (Skp1-Cullin-F-box) ubiquitin ligase complexes that mediate protein degradation, plays an important role at both G1-S and G2-M cell cycle transitions in yeast, and is highly conserved throughout eukaryotes. Plant SGT1 is required for both resistance (R) gene-mediated disease resistance and nonhost resistance to certain pathogens. Using virus-induced gene silencing (VIGS) in Nicotiana benthamiana, we demonstrate that SGT1 positively regulates the process of cell death during both host and nonhost interactions with various pathovars of Pseudomonas syringae. Silencing of NbSGT1 in N. benthamiana plants delays the induction of hypersensitive response (HR)-mediated cell death against nonhost pathogens and the development of disease-associated cell death caused by the host pathogen P. syringae pv. tabaci. Our results further demonstrate that NbSGT1 is required for Erwinia carotovora- and Sclerotinia sclerotiorum-induced disease-associated cell death. Overexpression of NbSGT1 in N. benthamiana accelerates the development of HR during R gene-mediated disease resistance and nonhost resistance. Our data also indicate that SGT1 is required for pathogen-induced cell death, but is not always necessary for the restriction of bacterial multiplication in planta. Therefore, we conclude that SGT1 is an essential component affecting the process of cell death during both compatible and incompatible plant-pathogen interactions.

Host Versus Nonhost Resistance: Distinct Wars with Similar Arsenals

“…For example, in Nicotiana benthamiana, the suppressor of the G2 allele of Sphase kinase-associated protein 1 (SGT1) has been known for the production of ROS and HR cell death against nonhost bacterial pathogens (Shibata et al 2011;Wang et al 2010). Also, SGT1 together with Rar1 (Required for Mla12 Resistance 1) is required for resistance responses mediated by NBS-LRR and other R proteins (Azevedo et al 2002;Peart et al 2002).…”

Involvement of SGT1 in COR-mediated signal transduction pathway leading to disease symptom development

“…However there was no significant difference in bacterial an essential component of common signaling pathway leading to cell death. 10,16,17 Interestingly, we were unable to demonstrate that SGT1 is a part of SCF COI complex and thereby plays a role in JA/COR signaling. 10 COR is shown to facilitate the entry of P. syringae into Arabidopsis tissue by suppressing the closure of stomata.…”

The six Tomato yellow leaf curl virus genes expressed individually in tomato induce different levels of plant stress response attenuation

“…The HSP90 co-chaperone SGT1 positively regulated CD (Wang et al 2010). In tomato, the downregulation of the HSP90 machinery causes severe necrosis on the stems of inoculated plants .…”