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Paeonia ostii is an emerging woody oil crop, but drought severely inhibits its growth and promotion in arid or semiarid areas, and little is known about the mechanism governing this inhibition. In this study, the full-length cDNA of a caffeoyl-CoA O-methyltransferase gene (CCoAOMT) from P. ostii was isolated, and determined to be comprised of 987 bp. PoCCoAOMT encoded a 247-amino acid protein, which was located in the nucleus and cytosol. Significantly higher PoCCoAOMT transcription was detected in P. ostii treated with drought stress. Subsequently, the constitutive overexpression of PoCCoAOMT in tobacco significantly conferred drought stress tolerance. Under drought stress, transgenic lines exhibited lower reactive oxygen species (ROS) accumulation, and higher antioxidant enzyme activities and photosynthesis. Moreover, the expression levels of senescence-associated genes were significantly downregulated, whereas the expression levels of lignin biosynthetic genes and PoCCoAOMT were significantly upregulated in transgenic lines. Similarly, transgenic lines produced significantly higher lignin, especially guaiacyl-lignin. These results suggest that PoCCoAOMT is a vital gene in promoting lignin synthesis and ROS scavenging to confer drought stress tolerance in P. ostii., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Seed viability is an important trait in agriculture which directly influences seedling emergence and crop yield. However, even when stored under optimal conditions, all seeds will eventually lose their viability. Our primary aims were to describe factors influencing seed deterioration, determine the morphological, physiological, and biochemical changes that occur during the process of seed ageing, and explore the mechanisms involved in seed deterioration. High relative humidity and high temperature are two factors that accelerate seed deterioration. As seeds age, frequently observed changes include membrane damage and the destruction of organelle structure, an increase in the loss of seed leachate, decreases of respiratory rates and ATP production, and a loss of enzymatic activity. These phenomena could be inter-related and reflect the general breakdown in cellular organization. Many processes can result in seed ageing; it is likely that oxidative damage caused by free radicals and reactive oxygen species (ROS) is primarily responsible. ROS can have vital interactions with any macromolecule of biological interest that result in damage to various cellular components caused by protein damage, lipid peroxidation, chromosomal abnormalities, and DNA lesions. Further, ROS may also cause programmed cell death by inducing the opening of mitochondrial permeability transition pores and the release of cytochrome C. Some repairs can occur in the early stages of imbibition, but repair processes fail if sufficient damage has been caused to critical functional components. As a result, a given seed will lose its viability and eventually fail to germinate in a relatively short time period., (Copyright © 2020 Elsevier Masson SAS. All rights reserved.)

SUMMARY: Drought is a detrimental environmental factor that restricts plant growth and threatens food security throughout the world. WRKY transcription factors play vital roles in abiotic stress response. However, the roles of IIe subgroup members from WRKY transcription factor family in soluble sugar mediated drought response are largely elusive. In this study, we identified a drought‐responsive IIe subgroup WRKY transcription factor, PoWRKY69, from Paeonia ostii. PoWRKY69 functioned as a positive regulator in response to drought stress with nucleus expression and transcriptional activation activity. Silencing of PoWRKY69 increased plants sensitivity to drought stress, whereas conversely, overexpression of PoWRKY69 enhanced drought tolerance in plants. As revealed by yeast one‐hybrid, electrophoretic mobility shift assay, and luciferase reporter assays, PoWRKY69 could directly bind to the W‐box element of fructose‐1,6‐bisphosphate aldolase 5 (PoFBA5) promoter, contributing to a cascade regulatory network to activate PoFBA5 expression. Furthermore, virus‐induced gene silencing and overexpression assays demonstrated that PoFBA5 functioned positively in response to drought stress by accumulating fructose to alleviate membrane lipid peroxidation and activate antioxidant defense system, these changes resulted in reactive oxygen species scavenging. According to yeast two‐hybrid, bimolecular fluorescence complementation, and firefly luciferase complementation imaging assays, valine‐glutamine 11 (PoVQ11) physically interacted with PoWRKY69 and led to an enhanced activation of PoWRKY69 on PoFBA5 promoter activity. This study broadens our understanding of WRKY69‐VQ11 module regulated fructose accumulation in response to drought stress and provides feasible molecular measures to create novel drought‐tolerant germplasm of P. ostii. Significance Statement: This manuscript identified a novel WRKY69‐VQ11 module that regulated fructose accumulation in response to drought stress, which provides feasible molecular measures to create novel drought‐tolerant germplasm of Paeonia ostii. [ABSTRACT FROM AUTHOR]

Drought is a detrimental environmental factor limiting sustainable agricultural development worldwide. Paeonia ostii , an oil-producing woody crop, while its endogenous mystery underlying this tolerance remains largely elusive to scholars. Herein, we reported that PoWRKY17, a WRKY transcription factor from IId subgroup, positively functioned in face of drought stress in P. ostii. PoWRKY17 expressed in significantly higher abundance when drought was applied. Silencing of PoWRKY17 substantially reduced drought resistance, with decreased leaf water content and protective enzyme activities, increased relative electric conductivity (REC), malondialdehyde (MDA) content, and reactive oxygen species (ROS) accumulation. On the contrary, overexpression of PoWRKY17 endowed plants with higher drought tolerance with opposite drought-relevant physiological indices. Notably, both PoWRKY17- silenced P. ostii and PoWRKY17- overexpressing plants showed changes in lignin content under drought stress. Based on this clue, we quantified the expression of lignin biosynthetic caffeoyl-CoA O -methyltransferase (CCoAOMT) gene in PoWRKY17 -silenced P. ostii and found that PoCCoAOMT expression was significantly repressed. Next, protein-gene interaction assays showed that PoWRKY17 interacted with PoCCoAOMT promoter by targeting the W-box element and activated PoCCoAOMT expression under drought stress, which has been early verified to act as a positive participant in P. ostii drought tolerance. This study broadens our understanding of WRKY-mediated lignin biosynthesis regulation in response to drought stress in plants. [Display omitted] • A drought-related WRKY transcription factor PoWRKY17 was identified in Paeonia ostii. • PoWRKY17 positively responded to drought stress with enhanced expression. • PoWRKY17 enhanced drought tolerance in plants by promoting lignin accumulation. • PoWRKY17 enhanced PoCCoAOMT expression by targeting the W-box element. [ABSTRACT FROM AUTHOR]

• PlMAPK1 was cloned in Paeonia lactiflora and could respond to high-temperature stress. • Overexpression of PlMAPK1 in yeast system boosted high-temperature tolerance. • Silence of PlMAPK1 made plant injury more severe under high-temperature stress. Herbaceous peony (Paeonia lactiflora Pall.) is a traditional famous flower in China that prefers cold climates and is not tolerant of high summer temperatures. Mitogen-activated protein kinase (MAPK) is widely involved in plant signal transduction to various environmental stresses. In order to clarify the role of PlMAPK1 in response to high-temperature stress, it was cloned, and its open reading frame was 1215 bp, encoding 405 amino acids. Quantitative real-time PCR (qRT-PCR) analysis showed that when the plant was severely damaged by high temperatures, the expression level of PlMAPK1 was at its peak. Moreover, based on a systematic study of exogenous yeast, it was found that the yeast strain overexpressing PlMAPK1 grew better than the control under high-temperature stress. In addition, PlMAPK1 was transiently silenced by virus induced gene silencing technology (VIGS) in P. lactiflora. And under high-temperature stress, the leaves of transgenic plants wilted significantly, the accumulation of reactive oxygen species increased and the photosynthetic capacity decreased significantly. These findings suggested that PlMAPK1 might play a positive regulatory role in the response of P. lactiflora to high-temperature stress, laying a theoretical groundwork for P. lactiflora high-temperature tolerance breeding. [ABSTRACT FROM AUTHOR]

• PlbHLH87 was cloned in Paeonia lactiflora and could respond to high-temperature stress. • PlbHLH87 was localized in the nucleus and exhibited transcriptional activation activity. • Overexpressing PlbHLH87 enhanced high-temperature tolerance, while silencing it caused severe damage. Herbaceous peony (Paeonia lactiflora Pall.) exhibits captivating floral displays, however, its intolerance to high-temperature stress has seriously inhibited its popularization in the middle and lower reaches of the Yangtze River and its southern regions in China. The bHLH transcription factor family is widely distributed in plants and plays a crucial role in stress response. In this study, a bHLH transcription factor PlbHLH87 was isolated from P. lactiflora , and it was exhibited nuclear localization and transcriptional activation ability, indicating its involvement in gene regulation. PlbHLH87 showed increased expression levels in response to high-temperature stress, and transgenic plants with PlbHLH87 overexpression showed strengthened high-temperature resistance, while plants with silenced PlbHLH87 suffered severe damage under high-temperature stress. Various physiological indices demonstrated that PlbHLH87 could help to reduce reactive oxygen species accumulation, maintain the integrity of cell membranes and protect Photosystem II. These findings highlighted the critical role of PlbHLH87 in conferring high-temperature stress tolerance, which would be useful for molecular breeding of enhanced high-temperature tolerance in P. lactiflora. [ABSTRACT FROM AUTHOR]