OsCOP1 regulates embryo development and flavonoid biosynthesis in rice (Oryza sativa L.)

Abstract

Key message Novel mutations of OsCOP1 were identified to be responsible for yellowish pericarp and embryo lethal phenotype, which revealed that OsCOP1 plays a crucial role in flavonoid biosynthesis and embryogenesis in rice seed. Abstract Successful production of viable seeds is a major component of plant life cycles, and seed development is a complex, highly regulated process that affects characteristics such as seed viability and color. In this study, three yellowish-pericarp embryo lethal (yel) mutants, yel-hc, yel-sk, and yel-cc, were produced from three different japonica cultivars of rice (Oryza sativa L). Mutant seeds had yellowish pericarps and exhibited embryonic lethality, with significantly reduced grain size and weight. Morphological aberrations were apparent by 5 days after pollination, with abnormal embryo development and increased flavonoid accumulation observed in the yel mutants. Genetic analysis and mapping revealed that the phenotype of the three yel mutants was controlled by a single recessive gene, LOC_Os02g53140, an ortholog of Arabidopsis thaliana CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1). The yel-hc, yel-sk, and yel-cc mutants carried mutations in the RING finger, coiled-coil, and WD40 repeat domains, respectively, of OsCOP1. CRISPR/Cas9-targeted mutagenesis was used to knock out OsCOP1 by targeting its functional domains, and transgenic seed displayed the yel mutant phenotype. Overexpression of OsCOP1 in a homozygous yel-hc mutant background restored pericarp color, and the aberrant flavonoid accumulation observed in yel-hc mutant was significantly reduced in the embryo and endosperm. These results demonstrate that OsCOP1 is associated with embryo development and flavonoid biosynthesis in rice grains. This study will facilitate a better understanding of the functional roles of OsCOP1 involved in early embryogenesis and flavonoid biosynthesis in rice seeds.

Genome-wide analysis and functional annotation of chromatin-enriched noncoding RNAs in rice during somatic cell regeneration

“…6 F; Additional file 1 : Fig. S6A), and their family members have been reported to regulate organ development [ 45 – 47 ]. No che-RNA-associated motif was detected in che-lncNAT OsCHENAT1709 .…”

Mutations in OsDET1, OsCOP10, and OsDDB1 confer embryonic lethality and alter flavonoid accumulation in Rice (Oryza sativa L.) seed

“…In addition, we previously identified three Arabidopsis “ fusca ”-like cop1 null mutants ( yel - hc , yel - sk , and yel - cc ) in rice. These mutants carry loss-of-function alleles of OsCOP1 and share several phenotypic characteristics with the yel - sdj mutant, including embryonic lethality and high-level flavonoid accumulation in the pericarp and embryo ( Kim et al, 2021 ). Similarly, the Arabidopsis det1 null mutant displays the phenotypic characteristics of strong cop1 mutant alleles, such as short hypocotyls, opened cotyledons, and anthocyanin accumulation ( McNellis et al, 1994 ; Misera et al, 1994 ; Pepper et al, 1994 ).…”

“…Previously, we reported the "fusca"-like cop1 null mutants in rice, which we named as yellowish-pericarp embryo lethal (yel), and showed that the corresponding gene, OsCOP1, regulates flavonoid biosynthesis and embryo development. However, the effect of COP1 mutation on embryo development and pigmentation in rice was different from that in Arabidopsis; unlike the Arabidopsis fus mutants, which exhibited seedling lethality and anthocyanin accumulation in the cotyledons, the rice yel mutants showed embryonic lethality and flavonoid accumulation in the embryo and pericarp (Kim et al, 2018(Kim et al, , 2021.…”

Flavonoids: Recent Advances and Applications in Crop Breeding

“…This not only turned the pericarp of the rice variety yellowish but also caused embryonic death. Moreover, this also reduced the size of the transgenic seeds [98]. According to a study, a total of 82 flavonoids have been chemically identified in transgenic rice seeds.…”