AUTHOR=Li Quanlin , Zhai Wenxue , Wei Jiaping , Jia Yanfeng 

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

JOURNAL=Frontiers in Genetics

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/genetics/articles/10.3389/fgene.2023.1111318

DOI=10.3389/fgene.2023.1111318

ISSN=1664-8021

ABSTRACT=<p>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 <italic>OsLTPL23</italic> were generated by CRISPR/Cas9-mediated genome editing, and <italic>osltpl23</italic> 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 <italic>osltpl23</italic> mutants. Transcript profiles in the germinating seeds exhibited that the abscisic acid (ABA)-responsive genes, <italic>OsABI3</italic> and <italic>OsABI5</italic>, and biosynthesis genes, <italic>OsNCED1</italic>, <italic>OsNCED2</italic>, <italic>OsNCED3</italic> and <italic>OsNCED4</italic>, are obviously upregulated in the <italic>osltpl23</italic> mutants compared to NIP plants, conversely, ABA metabolism genes <italic>OsABA8ox1</italic>, <italic>OsABA8ox2</italic> and <italic>OsABA8ox3</italic> are stepwise decreased. Further investigations found that <italic>osltpl23</italic> mutants displays weakened early seedling growth, with elevated gene expresssion of ABA catabolism genes and repressive transcription response of defence-related genes <italic>OsWRKY45, OsEiN3, OsPR1a</italic>, <italic>OsPR1b</italic> and <italic>OsNPR1</italic>. Integrated analysis indicated that <italic>OsLTPL23</italic> may exert an favorable effect on rice seed germination and early seedling growth <italic>via</italic> modulating endogenous ABA homeostasis. Collectively, our study provides important insights into the roles of <italic>OsLTPL23</italic>-mediated carbohydrate conversion and endogenous ABA pathway on seed germination and early seedling growth, which contributes to high-vigor seed production in rice breeding.</p>