Blue light promotes ascorbate synthesis by deactivating the PAS/LOV photoreceptor that inhibits GDP-L-galactose phosphorylase

Abstract

Ascorbate (vitamin C) is one of the most essential antioxidants in fresh fruits and vegetables. To get insights into the regulation of ascorbate metabolism in plants, a mutant producing ascorbate-enriched fruits was studied. The causal mutation, identified by a mapping-by-sequencing strategy, corresponded to a knock-out recessive mutation in a new class of photoreceptor named PAS/LOV protein (PLP, Solyc05g07020), which acts as a negative regulator of ascorbate biosynthesis in tomato. This trait was confirmed by CRISPR/Cas9 gene editing, and further found in all plant organs, including fruit that accumulated 2-3 times more ascorbate than in the WT. The functional characterization revealed that PLP interacted with the two isoforms of GDP-L-galactose phosphorylase (GGP), known as the controlling step of the L-galactose pathway of ascorbate synthesis. The interaction with GGP occurred in the cytoplasm and the nucleus, but was abolished when PLP was mutated. These results were confirmed by an optogenetic approach using an animal cell system, which additionally demonstrated that blue light modulated the PLP-GGP interaction. Assays performed in vitro with heterologously expressed GGP and PLP showed that PLP is a non-competitive inhibitor of GGP that is inactivated after blue light exposure. This discovery sheds light on the light-dependent regulation of ascorbate metabolism in plants.

GmPLP1 negatively regulates soybean resistance to high light stress by modulating photosynthetic capacity and reactive oxygen species accumulation in a blue light‐dependent manner

“…Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd., 21, 2625-2640especially when multiple stresses occur simultaneously, it will seriously damage the growth and yield of soybean. In our previous studies, we demonstrated that the expression level of GmPLP1 gene exhibits a distinct circadian rhythm and is significantly induced by fluctuating light(Li et al, 2018), which is consistent with the findings ofBournonville et al (2023). In thisª 2023 The Authors.…”

“…In our previous studies, we demonstrated that the expression level of GmPLP1 gene exhibits a distinct circadian rhythm and is significantly induced by fluctuating light (Li et al ., 2018), which is consistent with the findings of Bournonville et al . (2023). In this study, we discovered that the PLP protein can dynamically regulate soybean's resistance to high light stress by sensing varying intensities of blue light.…”

Enzyme‐based kinetic modelling of ASC–GSH cycle during tomato fruit development reveals the importance of reducing power and ROS availability

“…On the other hand, the analysis of ASC‐enriched fruits validated the kinetic model and highlighted that ASC fruit content was mainly regulated by its own synthesis (Fig. 3a) and not by import from leaves such as for photoassimilates (Gautier et al ., 2009) despite a light‐dependent regulation mechanism (Bournonville et al ., 2023). Nonetheless, the kinetic model showed an exponential accumulation of reduced ASC above a certain threshold, especially for young fruits.…”