Expression of Target Gene Hsp70 and Membrane Stability Determine Heat Tolerance in Chili Pepper

Abstract

<jats:p>Experiments were carried out to study the mechanisms for heat tolerance in chili pepper (<jats:italic>Capsicum annuum</jats:italic>). To assess these mechanisms, six genotypes were evaluated for cellular membrane thermostability (CMT) and for <jats:italic>HSP70</jats:italic> gene expression. The plants were grown in an experimental plant growth chamber. The mean value of CMT indicates that membrane integrity was not damaged by the high temperature treatment (50 °C) in most of the genotypes. The genotypes were classified as follows: heat-tolerant (greater than 60%), moderately tolerant (30% to 60%), and susceptible (less than 30%). The heat-tolerant plants recorded the highest CMTs at 89.27%, 88.03%, and 85.10% for AVPP0702, AVPP0116, and AVPP9905, respectively, which might be the reason for the change in their cell membrane thermostability. AVPP9703 and AVPP0002 showed CMTs of 15.87% and 18.43%, which might indicate their sensitivity to heat stress. Heat shock protein 70 kDa was identified and found to be differentially expressed under the heat stress. Under heat stress, significantly increased levels of the <jats:italic>HSP70</jats:italic> gene were detected after 2 h of temperature treatment at 42 °C, which indicated that this gene is quickly and sharply induced by heat shock. This was true for all genotypes tested, which were significantly up-regulated by more than 36.9-, 7.10-, 3.87-, and 3-fold for AVPP0702, AVPP0116, AVPP0002, and AVPP9703, respectively. The <jats:italic>HSP70</jats:italic> gene was found to be significantly down-regulated under heat stress in ‘Kulai’. AVPP0702, AVPP9905, and AVPP0116 could be considered as heat-tolerant genotypes, whereas ‘Kulai’ and AVPP9703 were found to be heat-sensitive genotypes in this investigation.</jats:p>

Growing Environment and Heat Treatment Effects on Intra- and Interspecific Pollination in Chile Pepper (Capsicum spp.)

“…In addition, in vitro heat treatment pollination success rate was also significantly correlated with pollination success rate during the winter season, which seems contradictory but could be explained by certain accessions having generally higher or lower pollination success rates, despite the growing season or heat treatment. For example, AVPP9905, a previously reported heat-tolerant line [34], was among the samples with the highest average pollination success rates when used as a male parent during the summer season (26%), the winter season (54%), under in vitro heat treatment (33%), and under no treatment (47%), while AVPP9823 was among the samples with the lowest average pollination success rates during the summer season (15%), the winter season (44%), under in vitro heat treatment (20%), and under no treatment (39%).…”

“…The response of chile pepper to high temperatures at the vegetative (generally seedling) [34,[39][40][41][42][43] and reproductive [23,24,26,44,45] stages during the growing season has been previously explored. In recent years, researchers have characterized differentially expressed genes in response to high-temperature stress in chile pepper [34,[39][40][41][42]. In vitro bioassays have been developed to effectively screen chile pepper accessions for heat tolerance [17,18,21].…”

A Molecular View of Plant Local Adaptation: Incorporating Stress-Response Networks

“…In their simplest form the genes that underlie these traits show low expression in the absence of stress but turn on when the plant senses environmental change. For instance, certain heat shock proteins are produced above only a certain temperature (170). Most stress responses that we have described fall into this category, though their associated costs vary.…”

Exogenous Methyl Jasmonate Improves Heat Tolerance of Perennial Ryegrass Through Alteration of Osmotic Adjustment, Antioxidant Defense, and Expression of Jasmonic Acid-Responsive Genes

“…Especially, as an essential regulator of protein, the Hsp70 has the tendency to maintain internal cell stability, protecting the injured organisms by enhancing the stability of mRNA and translating preferentially under heat condition (McGarry and Lindquist, 1985). Previous studies showed that overexpression of Hsp70 gene was leading to increasing the tolerance of Arabidopsis thaliana (Shinya et al, 2014), Capsicum annuum (Guo et al, 2014;Usman et al, 2015), Zea mays (Ristic et al, 1991), and O. sativa (Wang et al, 2014) under heat and drought stress.…”