Zaxinone Synthaseoverexpression modulates rice physiology and metabolism, improving growth and productivity under normal and low phosphate supply

Abstract

AbstractThe riceZaxinone Synthase (ZAS)gene encodes a carotenoid cleavage dioxygenase (CCD) that forms the apocarotenoid growth regulator zaxinone. Here, we generated and characterized constitutiveZAS-overexpressing rice lines, to better understandZASrole in determining zaxinone content and regulating growth and architecture.ZASoverexpression enhanced endogenous zaxinone level, promoted root growth and meristem size, and increased the number of productive tillers, leading to an up to 30% higher grain yield per plant. Hormone analysis revealed a decrease in strigolactone (SL) content, which we confirmed by rescuing the high-tillering phenotype through application of a SL analog. Metabolomics analysis revealed thatZASoverexpressing plants accumulate higher amounts of monosaccharide sugars, in line with transcriptome analysis. Moreover, transgenic plants showed higher carbon (C) assimilation rate and elevated root phosphate, nitrate and sulfate level, enhancing the tolerance towards low phosphate (Pi) and indicating a generally better nutrient uptake. Our study shows thatZASregulates hormone homeostasis and a combination of physiological processes to promote growth and grain yield, which makes this gene an excellent candidate for sustainable crop improvement.TeaserZaxinone Synthaseoverexpression modulates rice metabolism and physiology and improves growth and phosphate uptake.