Manipulation of photosensory and circadian signalling restricts phenotypic plasticity in response to changing environmental conditions in Arabidopsis

Plants exploit phenotypic plasticity to adapt their growth and development to prevailing environmental conditions. Interpretation of light and temperature signals are aided by the circadian system which provides a temporal context. Phenotypic plasticity provides a selective and competitive advantage in nature but is obstructive during large-scale, intensive agricultural practices since economically important traits (including vegetative growth and flowering time) can widely vary depending on local environmental conditions. This prevents accurate prediction of harvesting times and produces a variable crop. We sought to restrict phenotypic plasticity and circadian regulation by manipulating signalling systems that govern plants’ responses to environmental signals. Mathematical modelling of plant growth and development predicted reduced plant responses to changing environments when circadian and light signaling pathways were manipulated. We tested this hypothesis by utilising a constitutively-active allele of the plant photoreceptor phytochromeB, along with disruption of the circadian system via mutation of EARLY FLOWERING3. We found that these manipulations produced plants that were less responsive to light and temperature cues and which failed to anticipate dawn. These engineered plants have uniform vegetative growth and flowering time, demonstrating how phenotypic plasticity can be limited whilst maintaining plant productivity. This has significant implications for future agriculture in both open fields and controlled environments

Circadian clock factors regulate the first condensation reaction of fatty acid synthesis in Arabidopsis

Summary: The circadian clock regulates temporal metabolic activities, but how it affects lipid metabolism is poorly understood. Here, we show that the central clock regulators LATE ELONGATED HYPOCOTYL (LHY) and CIRCADIAN CLOCK ASSOCIATED 1 (CCA1) regulate the initial step of fatty acid (FA) biosynthesis in Arabidopsis. Triacylglycerol (TAG) accumulation in seeds was increased in LHY-overexpressing (LHY-OE) and decreased in lhycca1 plants. Metabolic tracking of lipids in developing seeds indicated that LHY enhanced FA synthesis. Transcript analysis revealed that the expression of genes involved in FA synthesis, including the one encoding β-ketoacyl-ACP synthase III (KASIII), was oppositely changed in developing seeds of LHY/CCA1-OEs and lhycca1. Chromatin immunoprecipitation, electrophoretic mobility shift, and transactivation assays indicated that LHY bound and activated the promoter of KASIII. Furthermore, phosphatidic acid, a metabolic precursor to TAG, inhibited LHY binding to KASIII promoter elements. Our data show a regulatory mechanism for plant lipid biosynthesis by the molecular clock