Phosphorylated transcription factor PuHB40 is involved in ROS-dependent anthocyanin biosynthesis in pear exposed to high-light stress

Abstract

ABSTRACTIn the context of global warming and climate change, as sessile organisms, plants are more vulnerable to environmental stresses than before. Stress-induced reactive oxygen species (ROS) accumulation results in plant cell damages and even cell death. Anthocyanins are important antioxidants that scavenge ROS to maintain ROS homeostasis. However, the mechanism underlying ROS-induced anthocyanin accumulation is unclear. In this study, we determined that the HD-Zip I family member PuHB40 mediates ROS-dependent anthocyanin biosynthesis under high-light stress. Specifically, PuHB40 is a transcription factor that induces PuMYB123-like/PubHLH3 complex for anthocyanin biosynthesis. The transcriptional activation by PuHB40 depends on its phosphorylation level, which is regulated by protein phosphatase 2A (PP2A). High ROS contents maintain the phosphorylation of PuHB40 at a high level, while also enhancing PuHB40-inducedPuMYB123-liketranscription by decreasingPuPP2AA2expression at the transcriptional and translational levels, ultimately leading to increased anthocyanin biosynthesis. Our study revealed the pathway regulating ROS-induced anthocyanin biosynthesis in pear, further clarifying the mechanism underlying abiotic stress-induced anthocyanin biosynthesis, which may have implications for improving plant stress tolerance.IN A NUTSHELLBackgroundVarious abiotic stresses, including high light, promotes the accumulation of anthocyanins in plants. Anthocyanins attenuate the negative effects of on photosynthesis and physiological metabolism of plants under high-light stress by absorbing excess light energy or by acting as an antioxidant to reduce ROS accumulation. Several reports have showed that ROS can stimulate anthocyanin accumulation, but whether the high-light induced anthocyanin accumulation depends on ROS is still under debate. Nevertheless, the underlying mechanism of ROS-dependent anthocyanin biosynthesis is still not clear.Question:What is the underlying molecular mechanism of high light stress-induced anthocyanin biosynthesis?FindingsWe found that various stresses-induced anthocyanin accumulation in pear plant is dependent on ROS. PuHB40 was the core TF involved in ROS-dependent anthocyanin biosynthesis under high-light stress, while PuMYB13-like is the key MYB TF for anthocyanin biosynthesis in ROS pathway. PuHB40 transcriptionally activates PuMYB123-like/PubHLH3 complex for promoting anthocyanin biosynthesis. The transcriptional activation by PuHB40 depends on its phosphorylation level, which is regulated by protein phosphatase 2A (PP2A). High ROS contents maintain the phosphorylation of PuHB40 at a high level, while also enhancing PuHB40-inducedPuMYB123-liketranscription by decreasingPuPP2AA2expression at the transcriptional and translational levels, ultimately leading to increased anthocyanin biosynthesis.Next stepsAn important task for next step is to explore whether PuHB40 regulation pathway is applicable in other stresses and provide insight into theoretical basis of abiotic stress-induced anthocyanin biosynthesis. In addition, investigate other post-translational modifications involved in ROS-dependent anthocyanin biosynthesis. Moreover, we will explore the effects of different stress levels on anthocyanin accumulation in pear fruits, and try to regulate pear fruit coloration by appropriate stress.