A multi-omics approach identifies <i>bHLH71-like</i> as a positive regulator of yellowing leaf pepper mutants exposed to high-intensity light

Abstract

Light quality and intensity can have a significant impact on plant health and crop productivity. Chlorophylls and carotenoids are classes of plant pigments that are responsible for harvesting light energy and protecting plants from the damaging effects of intense light. Our understanding of the role played by plant pigments in light sensitivity has been aided by light-sensitive mutants that change colors upon exposure to light of variable intensity. In this study, we conducted transcriptomic, metabolomic, and hormone analyses on a novel yellowing mutant of pepper (<i>yl1</i>) to shed light on the molecular mechanism that regulates the transition from green to yellow leaves in this mutant upon exposure to high-intensity light. Our results revealed greater accumulation of the carotenoid precursor phytoene and the carotenoids phytofluene, antheraxanthin, and zeaxanthin in <i>yl1</i> compared with wild-type plants under high light intensity. A transcriptomic analysis confirmed that enzymes involved in zeaxanthin and antheraxanthin biosynthesis were upregulated in <i>yl1</i> upon exposure to high-intensity light. We also identified a single basic helix-loop-helix (bHLH) transcription factor, <i>bHLH71-like</i>, that was differentially expressed and positively correlated with light intensity in <i>yl1</i>. Silencing of <i>bHLH71-like</i> in pepper plants suppressed the yellowing phenotype and led to reduced accumulation of zeaxanthin and antheraxanthin. We propose that the yellow phenotype of <i>yl1</i> induced by high light intensity could be caused by an increase in yellow carotenoid pigments, concurrent with a decrease in chlorophyll accumulation. Our results also suggest that <i>bHLH71-like</i> functions as a positive regulator of carotenoid biosynthesis in pepper.