Rice lipid transfer protein, OsLTPL23, controls seed germination by regulating starch-sugar conversion and ABA homeostasis.

Seed germination is vital for ensuring the continuity of life in spermatophyte. High-quality seed germination usually represents good seedling establishment and plant production. Here, we identified OsLTPL23, a putative rice non-specific lipid transport protein, as an important regulator responsible for seed germination. Subcellular localization analysis confirmed that OsLTPL23 is present in the plasma membrane and nucleus. The knockout mutants of were generated by CRISPR/Cas9-mediated genome editing, and lines significantly germinated slower and lower than the Nipponbare (NIP). Starch and soluble sugar contents measurement showed that OsLTPL23 may have alpha-amylase inhibitor activity, and high soluble sugar content may be a causal agent for the delayed seed germination of mutants. Transcript profiles in the germinating seeds exhibited that the abscisic acid (ABA)-responsive genes, and , and biosynthesis genes, , , and , are obviously upregulated in the mutants compared to NIP plants, conversely, ABA metabolism genes , and are stepwise decreased. Further investigations found that mutants displays weakened early seedling growth, with elevated gene expresssion of ABA catabolism genes and repressive transcription response of defence-related genes , and . Integrated analysis indicated that may exert an favorable effect on rice seed germination and early seedling growth modulating endogenous ABA homeostasis. Collectively, our study provides important insights into the roles of -mediated carbohydrate conversion and endogenous ABA pathway on seed germination and early seedling growth, which contributes to high-vigor seed production in rice breeding.