Biochemical and molecular responses of herbaceous peony to high temperature stress

Abstract

To clarify the theoretical basis of the differences in high temperature stress tolerance among herbaceous peony (Paeonia lactiflora Pall.), we investigated the heat injury index of twelve P. lactiflora cultivars. Of these, heat-tolerant 'Zifengyu' and moderately heat-tolerant 'Hongyanzhenghui' were selected to study the biochemical and molecular responses to high temperature stress. 'Zifengyu' had reduced malondialdehyde (MDA) content, increased soluble sugar, chlorophyll (Chl) a, Chl b, Chl a + b. and carotenoid contents, as well as elevated antioxidant enzymes activities, photosynthetic rate (Pn), transpiration rate (Tr) and relatively intact cellular structures compared with 'Hongyanzhenghui', especially when the temperature was the highest. Additionally, we isolated partial cDNAs of two heat shock protein genes (HSP60 and HSP90) from P. lactiflora, which were 880-bp and 1077-bp nucleotides in length, respectively. The expression levels of PlHSP60, PlHSP70 and PlHSP90 were lower in 'Zifengyu' than in 'Hongyanzhenghui' for the first three of four developmental stages examined. These results indicated that heat-tolerant P. lactiflora cultivar could effectively scavenge reactive oxygen species (ROS), protect cellular structures, reduce thermal damage and delay the death of plants by enhancing antioxidant enzymes activities and HSP expression under high temperature stress. These findings provide a theoretical basis for breeding heat-tolerant P. lactiflora cultivars.Key words: herbaceous peony, high temperature stress, physiological mechanism, heat shock protein.Résumé : Afin d'éclaircir les fondements théoriques expliquant la tolérance variable des pivoines de Chine (Paeonia lactiflora Pall.) au stress thermique, les chercheurs ont examiné l'indice des dommages causés par la chaleur de douze cultivars. Parmi ceux-ci, on a retenu les variétés Zifengyu, résistante à la chaleur, et Hongyanzhenghui, modérément tolérante à la chaleur, pour approfondir les réactions biochimiques et moléculaires au stress thermique. Comparativement à Hongyanzhenghui, la variété Zifengyu se caractérise par une plus faible teneur en malondialdéhyde (MDA), une concentration plus élevée de sucres solubles, de chlorophylle (Chl) a, de Chl b, de Chl a + b et de caroténoïdes, ainsi qu'une hausse de l'activité des enzymes antioxydants, du taux de photosynthèse (Pn), du taux de transpiration (Tr) et de la quantité d'organites cellulaires relativement intacts, surtout quand la température atteint un maximum. Par ailleurs, les auteurs ont isolé une partie de l'ADNc des gènes codant deux protéines de choc thermique (HSP60 et HSP90) chez P. lactiflora, dont lalongueur respective est de 880-bp et de 1,077-bp nucléotides. Le taux d'expression des gènes PlHSP60, PlHSP70 et PlHSP90 était plus faible chez Zifengyu que chez Hongyanzhenghui au cours des trois premiers stades de développement sur les quatre examinés. Ces résultats indiquent que le cultivar de P. lactiflora résistant à la chaleur pourrait neutraliser les dérivés réactifs de l'oxygè...

Overexpression of herbaceous peony HSP70 confers high temperature tolerance

“…Chen et al [38] observed chloroplast ultrastructural changes in C. medica using transmission electron microscopy and found chloroplast ultrastructural alterations, including their swelling, matrix zone expanding and lamella structure loosening. In moderately heat-tolerant P. lactiflora , few intact cellular structures were observed, most of the chloroplasts were swollen and assumed a near spherical shape, and their membranes were decomposed, which caused leakage of the grana lamellaes under high temperature stress [20]. In this study, PlHSP70 -overexpressing transgenic lines had more intact cell membranes, chloroplasts and starch grains and fewer plastoglobulis than WT, which was consistent with our observation of the yellow leaves in WT.…”

“…Under high temperature stress, HSPs are synthesized and accumulated, and their contents are increased when the plants experience either abrupt or gradual increases in temperature [31]. In our previous studies, the expression levels of PlHSP70 were all detected in P. lactiflora subjected to long-term high temperature stress, and the results showed that they all increased gradually in the early stages and then decreased [20, 21]. Whereas in this study, the potted P. lactiflora was treated under short-term high temperature stress, the expression level of PlHSP70 increased gradually with the treatment, and no decline was observed.…”

Exogenous trehalose confers high temperature stress tolerance to herbaceous peony by enhancing antioxidant systems, activating photosynthesis, and protecting cell structure

“…P. lactiflora favors sunny environments while avoiding summer high temperature, often leading to high temperature stress in south China environments (Zhang et al 2016). In this respect, the effects of high temperature stress on P. lactiflora physiology and biochemistry were investigated, and it was found that high temperature-tolerant P. lactiflora cultivars could effectively reduce stress damage by enhancing antioxidant enzyme activities and heat shock protein gene expression (Wu et al 2016). Moreover, transcriptome and digital gene expression analysis of P. lactiflora were used to screen for thermo-tolerant-related differentially expressed genes (Hao et al 2016).…”

Germplasm resources and genetic breeding of Paeonia: a systematic review

“…Research on the abiotic stress resistance of Paeonia has mainly focused on plant responses to low versus high temperature, drought, salt, and heavy metals. Under high-temperature (35.75/27.5°C, average daily maximum/minimum temperature) stress, heatresistant P. lactiflora 'Zifengyu' showed enhanced activity of antioxidant enzymes (superoxide dismutase, peroxidase, and catalase) and the expression of HSP, which removed reactive oxygen species effectively and prevented plants from dying 169,170 . HSP70-overexpressing transgenic plants were tolerant to high temperature 171,172 .…”