Antioxidant Enzymatic Activities and Gene Expression Associated with Heat Tolerance in the Stems and Roots of Two Cucurbit Species (“Cucurbita maxima” and “Cucurbita moschata”) and Their Interspecific Inbred Line “Maxchata”

Abstract

The elucidation of heat tolerance mechanisms is required to combat the challenges of global warming. This study aimed to determine the antioxidant enzyme responses to heat stress, at the enzymatic activity and gene expression levels, and to investigate the antioxidative alterations associated with heat tolerance in the stems and roots of squashes using three genotypes differing in heat tolerance. Plants of heat-tolerant “C. moschata”, thermolabile “C. maxima” and moderately heat-tolerant interspecific inbred line “Maxchata” genotypes were exposed to moderate (37 °C) and severe (42 °C) heat shocks. “C. moschata” exhibited comparatively little oxidative damage, with the lowest hydrogen peroxide (H2O2), superoxide (O2−) and malondialdehyde (MDA) contents in the roots compared to stems, followed by “Maxchata”. The enzyme activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) and peroxidase (POD) were found to be increased with heat stress in tolerant genotypes. The significant inductions of FeSOD, MnSOD, APX2, CAT1 and CAT3 isoforms in tolerant genotypes suggested their participation in heat tolerance. The differential isoform patterns of SOD, APX and CAT between stems and roots also indicated their tissue specificity. Furthermore, despite the sequence similarity of the studied antioxidant genes among “C. maxima” and “Maxchata”, most of these genes were highly induced under heat stress in “Maxchata”, which contributed to its heat tolerance. This phenomenon also indicated the involvement of other unknown genetic and/or epigenetic factors in controlling the expression of these antioxidant genes in squashes, which demands further exploration.

Effects of individual and combined heat and drought stress during seed filling on the oxidative metabolism and yield of chickpea (Cicer arietinum) genotypes differing in heat and drought tolerance

“…In our study, the chickpeas had increased activity of SOD (catalyses dismutation of superoxides), and CAT (dissociates hydrogen peroxide under individual heat or drought stress), which was in accordance with the rise in MDA and H 2 O 2 in leaves and seeds. These findings concur with studies on drought-stressed plants of wheat (Devi et al 2012), soybean (Akitha Devi and Giridhar 2015) and hyacinth bean (Rai et al 2015), and heat-stressed plants of chickpea , wheat (Kumar et al 2013a;Wang et al 2015) and cucurbit species (Ara et al 2013). In the combined heat + drought stress treatment, tolerant genotypes had higher CAT activity in leaves and seeds than sensitive genotypes.…”

Transcriptional Profiling of Resistant and Susceptible Buffalograsses in Response to Blissus occiduus (Hemiptera: Blissidae) Feeding

“…In addition, two catalases were upregulated in Prestige (Table 4) and one downregulated in 378 (Table 5) at 7 d after chinch bug introduction. The upregulated catalase transcript, pre_comp605149_c0_ seq1, has sequence identity to catalase genes identified in Cucurbita maxima Duchesne (identity: 45%, E value: 1e-10) in response to heat stress (Ara et al 2013) and Solanum tuberosum L. (identity: 47%, E value: 8e-11) (Niebel et al 1995) that is induced in response to nematodes and bacterial infection.…”

Elucidation of Abiotic Stress Signaling in Plants

“…The antioxidant defense mechanisms play an essential role in the heat stress adaptation, and its strength associates with acquisition of thermotolerance . Also, higher ascorbic acid content or activities of CAT and SOD correlate with the capacity to acquire thermotolerance (Ara et al 2013 ;.…”