Powdery mildew (PM), which is mainly caused by Podosphaera xanthii , 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 SGT1 ( suppressor of the G2 allele of skp1 ), 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 ( Cucurbita moschata ) inbred line infected with PM. In this study, we have characterized this SGT1 homolog in C. moschata , and investigated its effects on biotic stress resistance. Subcellular localization results revealed that CmSGT1 is present in the nucleus. Additionally, CmSGT1 expression levels in the PM-resistant material was strongly induced by PM, salicylic acid (SA) and hydrogen peroxide (H 2 O 2 ). In contrast, SA and H 2 O 2 downregulated CmSGT1 expression in the PM-susceptible material. The ethephon (Eth) and methyl jasmonate (MeJA) treatments upregulated CmSGT1 expression in both plant materials. The constitutive overexpression of CmSGT1 in Nicotiana benthamiana ( N. benthamiana ) minimized the PM symptoms on the leaves of PM-infected seedlings, accelerated the onset of cell necrosis, and enhanced the accumulation of H 2 O 2 . Furthermore, the expression levels of PR1a and PR5 , which are SA signaling transduction markers, were higher in the transgenic plants than in wild-type plants. Thus, the transgenic N. benthamiana plants were significantly more resistant to Erysiphe cichoracearum than the wild-type plants. This increased resistance was correlated with cell death, H 2 O 2 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 N. benthamiana plants than in the wild-type plants in response to infections by the pathogens responsible for bacterial wilt and scab. Therefore, CmSGT1 -overexpressing N. benthamiana 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.

No abstract

No abstract

The low propagation coefficient was a main obstacle in tree peony regeneration for a long time. Here, we present a new plantlet regenernation system to significantly improve the propagation coefficien in tree peony regeneration by lateral buds exsectting and engraving. The proceduce are briefly as follows: (1)The medium for proliferation was WPM + 6-BA3.0mg/L + IAA 0.2mg/L, with the proliferation rate up to 787.05%; (2)The medium for plantlets rooting was 1/2 WPM medium supplemented with NAA 1.0 mg/L and IBA 4.0 mg/L which obtained 81.33% rooting rate. Compared with the control, the adventitious buds induction rate was significantly increased with the maximum reaching 96% and the number of adventitious buds were increased by 2.6-4.8 times through cutting. The plantlets were successfully transplanted to potting and the survival rate of transplanted plantlets was 90%.

No abstract