Triose phosphate export from chloroplasts and cellular sugar content regulate anthocyanin biosynthesis during high light acclimation

Plants have evolvedmultiple strategies to cope with rapid changes in the environment.During high light(HL)acclimation,the biosynthesis of photoprotective flavonoids,such as anthocyanins,is induced.However,the exact nature of the signal and downstreamfactors forHL induction of flavonoid biosynthesis(FB)is still under debate.Here,we show that carbon fixation in chloroplasts,subsequent export of photosynthates by triose phosphate/phosphate translocator(TPT),and rapid increase in cellular sugar content permit the transcriptional and metabolic activation of anthocyanin biosynthesis during HL acclimation.In combination with genetic and physiological analysis,targeted and whole-transcriptome gene expression studies suggest that reactive oxygen species and phytohormones play only a minor role in rapid HL induction of the anthocyanin branch of FB.In addition to transcripts of FB,sugar-responsive genes showed delayed repression or induction in tpt-2 during HL treatment,and a significant overlapwith transcripts regulated by SNF1-related protein kinase 1(SnRK1)was observed,including a central transcription factor of FB.Analysis of mutants with increased and repressed SnRK1 activity suggests that sugar-induced inactivation of SnRK1 is required for HL-mediated activation of anthocyanin biosynthesis.Our study emphasizes the central role of chloroplasts as sensors for environmental changes as well as the vital function of sugar signaling in plant acclimation.

A Phelipanche ramosa KAI2 protein perceives strigolactones and isothiocyanates enzymatically

Phelipanche ramosa is an obligate root-parasitic weed that threatens major crops in central Europe.In order to germinate,it must perceive various structurally divergent host-exuded signals,including isothiocyanates(ITCs)and strigolactones(SLs).However,the receptors involved are still uncharacterized.Here,we identify five putative SL receptors in P.ramosa and show that PrKAI2d3 is involved in the stimulation of seed germination.We demonstrate the high plasticity of PrKAI2d3,which allows it to interact with different chemicals,including ITCs.The SL perception mechanism of PrKAI2d3 is similar to that of endogenous SLs in non-parasitic plants.We provide evidence that PrKAI2d3 enzymatic activity confers hypersensitivity to SLs.Additionally,we demonstrate that methylbutenolide-OH binds PrKAI2d3 and stimulates P.ramosa germination with bioactivity comparable to that of ITCs.This study demonstrates that P.ramosa has extended its signal perception system during evolution,a fact that should be considered for the development of specific and efficient biocontrol methods.