SsSGP1 peptide regulates chlorophyll degradation in sugarcane through ethylene and peroxidase pathways

Abstract

Chlorophylls, the major plant pigments involved in photosynthesis, are essential for sucrose production in sugarcane (Saccharum officinarum L.). However, limited information is available on the regulatory mechanism underlying chlorophyll biosynthesis and degradation in sugarcane. Ethylene and peroxidase have been known to regulate chlorophyll degradation, but the upstream regulators of these factors involved in chlorophyll degradation have not been characterized. This study reports an SsSGP1 peptide hormone (the peptide with a highly conserved SGP-rich C-terminus motif) in sugarcane that regulates chlorophyll degradation. Using peptide treatment and whole-genome structural, transcriptomic, physiological, and biochemical analyses, this study demonstrated the function of the sugarcane SsSGP1 peptide in leaf yellowing and chlorophyll degradation. Further investigation of the evolutionary relationships of SGP peptides in 20 plant species (7 monocots and 13 dicots) led to the identification of 104 SGP peptide precursors, which were divided into two subfamilies. Whole-genome structural analysis revealed that the promoters of SGP peptides were enriched in several light- and stress-responsive cis-acting elements. Transcriptomic, physiological, and biochemical analyses suggested that SsSGP1 peptides participate in chlorophyll degradation by regulating ethylene and peroxidase pathways. Inhibitor experiments further verified this regulatory mechanism. Overall, this study demonstrated a novel function of the SsSGP1 peptide in regulating chlorophyll degradation through ethylene and peroxidase pathways in sugarcane.