Mutations on ent-kaurene oxidase 1 encoding gene attenuate its enzyme activity of catalyzing the reaction from ent-kaurene to ent-kaurenoic acid and lead to delayed germination in rice

Abstract

Rice seed germination is a critical step that determines its entire life circle, with seeds failing to germinate or pre-harvest sprouting both reduce grain yield. Nevertheless, the mechanisms underlying this complex biological event remain unclear. Previously, gibberellin has been shown to promote seed germination. In this study, a delayed seed germination rice mutant was obtained through screening of the EMS induced mutants. Besides of delayed germination, it also shows semi-dwarfism phenotype, which could be recovered by exogenous GA. Through re-sequencing on the mutant, wild-type and their F 2 populations, we identified two continuous mutated sites on ent-kaurene oxidase 1 (OsKO1) gene, which result in the conversion from Thr to Met in the cytochrome P450 domain. Genetic complementary analysis and enzyme assay verified that the mutations in OsKO1 gene block the biosynthesis of GA and result in the defect phenotypes. Further analyses proved that OsKO1 could catalyze the reaction from ent-kaurene into ent-kaurenoic acid in GA biosynthesis mainly at seed germination and seedling stages, and the mutations decrease its activity to catalyze the step from ent-kaurenol to ent-kaurenoic acid in this reaction. Transcriptomic and proteomic data indicate that the defect on GA biosynthesis decreases its ability to mobilize starch and attenuate ABA signaling, therefore delay the germination process. The results provide some new insights into both GA biosynthesis and seed germination regulatory pathway in rice.

The Current Status of Research on Gibberellin Biosynthesis

“…2004 , Chen et al. 2019 , Zhang et al. 2020 ), while OsKO4 (CYP701A8) hydroxylates ent -kaurene and related diterpenes at the 3α position, which is in close proximity to C-19 ( Wang et al.…”

“…2012 ). By coupling the N-terminal regions to GFP, Zhang et al. (2020) showed that OsKO2, similar to AtKO, is located in the plasmid outer membrane, whereas OsKO1 is present in the plastid and endomembranes.…”

The Candidate Genes Underlying a Stably Expressed QTL for Low Temperature Germinability in Rice (Oryza sativa L.)

“…The previous studies reported that gibberellins (GAs) play important roles in seed germination, stem elongation, and flower development (Yamaguchi and Kamiya 2000 ; Olszewski et al 2002 ). Recent studies demonstrated that genes involving in GA synthesis, OsGA20ox1 , OsGA20ox2 and OsKO1 promotes germination and enhances plant height in rice (Abe et al 2012 ; Ye et al 2015 ; Zhang et al 2020 ), while QTLs for seedling height and seed dormancy co-located with OsGA20ox1 (Abe et al 2012 ) and OsGA20ox2 (Ye et al 2015 ), respectively. Therefore, it could be possible that some LTG QTLs enhance seed germination under low temperature, and also contribute to increase in plant height, such QTLs could not be used in rice breeding for direct-seeding due to the risk of lodging.…”

A New Intra-Specific and High-Resolution Genetic Map of Eggplant Based on a RIL Population, and Location of QTLs Related to Plant Anthocyanin Pigmentation and Seed Vigour

“…Good candidates for future studies might also be other genes in the same region encoding an Ent-kaurene oxidase and two B3 domain proteins, all involved in GA biosynthesis: the latter are regulating factors of the pathway in which the former is a key enzyme, and it is reported that suppressive mutations in the coding region of both genes cause a delay in seed germination and seedling development [94,95].…”