Abstract
SBP-box (Squamosa-promoter binding protein) genes are a type of plant-specific transcription factor and play important roles in plant growth, signal transduction and stress response. However, little is known about the SBP-box genes in pepper (CaSBP), especially in the process of Phytophthora capsici infection. In this study, a novel gene (CaSBP12) was selected from the CaSBP gene family, which was isolated from the pepper genome database in our previous study. The CaSBP12 gene was located in the nucleus of the cell and its silencing in the pepper plant enhanced the defense response against Phytophthora capsici infection. After inoculation with Phytophthora capsici, the root activity of the CaSBP12-silenced plants is compared to control plants, while malondialdehyde (MDA) content is compared viceversa. Additionally, the expression of defense related genes (CaPO1, CaSAR8.2, CaBPR1, and CaDEF1) in the silenced plants were induced to different degrees and the peak of CaSAR8.2 and CaBPR1 were higher than that of CaDEF1. The CaSBP12 over-expressed Nicotiana benthamiana plants were more susceptible to Phytophthora capsici infection with higher EC (electrical conductivity) and MDA contents as compared to the wild-type. The relative expression of defense related genes (NbDEF, NbNPR1, NbPR1a, and NbPR1b) in transgenic and wild-type Nicotiana benthamiana plants were induced, especially the NbPR1a and NbPR1b. In conclusion, these results indicate that CaSBP12 gene negative regulates the defense response against Phytophthora capsici infection which suggests their potentially significant role in plant defense. To our knowledge, this is the first report on CaSBP gene which negative regulate defense response.
Highlights
Pepper (Capsicum annuum L.), widely cultivated throughout the world, is an important vegetable crop with high economic value, but it is prone to damage by diseases and insects, especially Phytophthora blight caused by a pathogen Phytophthora capsici (P. capsici) [1]
The results indicated that the control 35S::GFP exhibited GFP signals in the whole cell, including the nucleus, cytoplasm, cell membrane, and cell wall, while 35S::CaSBP12::GFP only exhibited GFP signals in the nucleus (Figure 1)
The expression of the NbDEF was induced in wild-type lines at days two and four, while there was no obvious change in transgenic lines except Int. dJ.aMyool.nSeci.a2n0d19f,o2u0r, .48These results indicated that the CaSBP12 plays a negative regulatory role in plant 11 of 20 defense response against P. capsici
Summary
Pepper (Capsicum annuum L.), widely cultivated throughout the world, is an important vegetable crop with high economic value, but it is prone to damage by diseases and insects, especially Phytophthora blight caused by a pathogen Phytophthora capsici (P. capsici) [1]. The function of the SBP-box family genes in pepper against the infection of P. capsici is unknown to date. Capana10g000886) with an open reading frame of 900bp, encoding 299 amino acids is a SBP-box gene in the pepper plant. It contains a highly conserved DNA-binding domain termed the SBP domain. The expression of CaSBP12 can be inhibited by the salicylic acid (SA) and methyl jasmonate (MeJA) synthesis inhibitor and induced by SA and MeJA [18] We selected this gene to further elucidate its function against P. capsici infection and its localization in the cell
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