Improved Powdery Mildew Resistance of Transgenic Nicotiana benthamiana Overexpressing the Cucurbita moschata CmSGT1 Gene

• Published in: Frontiers in plant science Vol. 10; p. 955
• Main Authors: Guo, Wei-Li, Chen, Bi-Hua, Guo, Yan-Yan, Yang, He-Lian, Mu, Jin-Yan, Wang, Yan-Li, Li, Xin-Zheng, Zhou, Jun-Guo
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Media S.A 25-07-2019
• Subjects: CmSGT1; Cucurbita moschata Duch; functional analysis; N. benthamiana; Plant Science; powdery mildew; CmSGT1; powdery mildew; functional analysis; N. benthamiana; Cucurbita moschata Duch
• ISSN: 1664-462X; 1664-462X
• DOI: 10.3389/fpls.2019.00955

Powdery mildew (PM), which is mainly caused by
, is a serious biotrophic pathogen disease affecting field-grown and greenhouse-grown cucurbit crops worldwide. Because fungicides poorly control PM, the development and cultivation of PM-resistant varieties is critical. A homolog of
(
), which encodes a key component of the plant disease-associated signal transduction pathway, was previously identified through a transcriptomic analysis of a PM-resistant pumpkin (
) inbred line infected with PM. In this study, we have characterized this
homolog in
, and investigated its effects on biotic stress resistance. Subcellular localization results revealed that CmSGT1 is present in the nucleus. Additionally,
expression levels in the PM-resistant material was strongly induced by PM, salicylic acid (SA) and hydrogen peroxide (H
O
). In contrast, SA and H
O
downregulated
expression in the PM-susceptible material. The ethephon (Eth) and methyl jasmonate (MeJA) treatments upregulated
expression in both plant materials. The constitutive overexpression of
in
(
) minimized the PM symptoms on the leaves of PM-infected seedlings, accelerated the onset of cell necrosis, and enhanced the accumulation of H
O
. Furthermore, the expression levels of
and
, which are SA signaling transduction markers, were higher in the transgenic plants than in wild-type plants. Thus, the transgenic
plants were significantly more resistant to
than the wild-type plants. This increased resistance was correlated with cell death, H
O
accumulation, and upregulated expression of SA-dependent defense genes. However, the chlorosis and yellowing of plant materials and the concentration of bacteria at infection sites were greater in the transgenic
plants than in the wild-type plants in response to infections by the pathogens responsible for bacterial wilt and scab. Therefore,
-overexpressing
plants were hypersensitive to these two diseases. The results of this study may represent valuable genetic information for the breeding of disease-resistant pumpkin varieties, and may also help to reveal the molecular mechanism underlying CmSGT1 functions.