Isolation and function analysis of herbaceous peony bHLH transcription factor PlbHLH87 in response to high-temperature stress

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.