OsRDH modulates multiple grain quality traits and contributes to rice seed germination and root growth development

Retinol dehydrogenase (RDH) catalyzes key steps in retinol-associated metabolic pathways in animals and has been implicated in multiple physiological processes in plants. Despite this, the contribution of the rice RDH gene (OsRDH) to plant development and grain quality formation has not been clearly defined. In earlier work, the important quality trait gene OsGAPC3 was isolated and cloned from rice. Through an in-depth investigation of the molecular regulation mechanisms underlying OsGAPC3, transcriptomic sequencing analysis revealed a marked upregulation of OsRDH expression in the Osgapc3 mutant. Subsequent studies demonstrated that OsRDH is constitutively expressed in rice, with its encoded protein localized in the chloroplasts. Loss-of-function mutation of OsRDH resulted in altered endosperm storage organization: protein bodies in mutant grains were reduced in size, accompanied by substantial decreases in total protein accumulation and essential amino acid content, ultimately diminishing grain nutritional value. In contrast, grain morphology was favorably modified, with elongated grains and pronounced reductions in both the extent and severity of endosperm chalkiness. These changes were associated with a more compact arrangement of starch granules, leading to improved grain appearance. Notably, the amylose content in Osrdh mutant rice was significantly lower, while milled rice yield was significantly higher, contributing to improvements in both processing quality and cooking quality. At the physiological level, disruption of OsRDH perturbed the transcription of genes involved in gibberellin (GA) and abscisic acid (ABA) metabolic pathways, thereby influencing seed germination behavior, root growth dynamics. Thus, these results demonstrate that OsRDH is an important quality trait gene with multiple biological functions, and is involved in various biological processes such as rice seed germination and root growth and development. Simultaneously, OsRDH represents a valuable target for the genetic improvement of grain appearance, processing performance, and cooling/eating quality through molecular breeding strategies.