CaHSP18.1a, a Small Heat Shock Protein from Pepper (Capsicum annuum L.), Positively Responds to Heat, Drought, and Salt Tolerance

Abstract

Pepper is a thermophilic crop, shallow-rooted plant that is often severely affected by abiotic stresses such as heat, salt, and drought. The growth and development of pepper is seriously affected by adverse stresses, resulting in decreases in the yield and quality of pepper crops. Small heat shock proteins (s HSPs) play a crucial role in protecting plant cells against various stresses. A previous study in our laboratory showed that the expression level of CaHSP18.1a was highly induced by heat stress, but the function and mechanism of CaHSP18.1a responding to abiotic stresses is not clear. In this study, we first analyzed the expression of CaHSP18.1a in the thermo-sensitive B6 line and thermo-tolerant R9 line and demonstrated that the transcription of CaHSP18.1a was strongly induced by heat stress, salt, and drought stress in both R9 and B6, and that the response is more intense and earlier in the R9 line. In the R9 line, the silencing of CaHSP18.1a decreased resistance to heat, drought, and salt stresses. The silencing of CaHSP18.1a resulted in significant increases in relative electrolyte leakage (REL) and malonaldehyde (MDA) contents, while total chlorophyll content decreased under heat, salt, and drought stresses. Overexpression analyses of CaHSP18.1a in transgenic Arabidopsis further confirmed that CaHSP18.1a functions positively in resistance to heat, drought, and salt stresses. The transgenic Arabidopsis had higherchlorophyll content and activities of superoxide dismutase, catalase, and ascorbate peroxidase than the wild type (WT). However, the relative conductivity and MDA content were decreased in transgenic Arabidopsis compared to the wild type (WT). We further showed that the CaHSP18.1a protein is localized to the cell membrane. These results indicate CaHSP18.1a may act as a positive regulator of responses to abiotic stresses.

Small Heat Shock Protein (sHSP) Gene Family from Sweet Pepper (Capsicum annuum L.) Fruits: Involvement in Ripening and Modulation by Nitric Oxide (NO)

“…More recently, the expression analysis of CaHSP18.1a (named CasHPS29 in Table 1 and expressed in fruit) in two pepper lines with different sensitivities to temperature (the thermo-sensitive B6 line and thermo-tolerant R9 line) showed that CaHSP18.1a is induced under heat stress, salt, and drought stress in both lines. Furthermore, the overexpression of CaHSP18.1a in Arabidopsis evidenced that this gene provides an increased resistance under these stresses since this transgenic Arabidopsis plants had also higher activity of some antioxidant enzymes, including catalase, SOD, and ascorbate peroxidase [ 63 ].…”

Advances in Molecular Breeding of Vegetable Crops

“…A small heat shock protein CaHSP18.1a was isolated and charactered from pepper [11]. Liu et al demonstrated that CaHSP18.1a was sensitive to heat stress and showed high expression levels in thermo-tolerant line.…”