Targeted mutagenesis of POLYAMINE OXIDASE 5 that negatively regulates mesocotyl elongation enables the generation of direct-seeding rice with improved grain yield

Abstract

Under conditions of labor or resource scarcity, direct seeding, rather than transplantation, is the preferred mode of rice (Oryza sativa) cultivation. This approach requires varieties that exhibit uniform seedling emergence. Mesocotyl elongation (ME), the main driver of rapid emergence of rice seedlings from soil, is enhanced by darkness and inhibited by light. Plant polyamine oxidases (PAOs) oxidize polyamines (PAs) and release H 2 O 2 . Here, we established that OsPAO5 expression in rice seedlings is increased in the presence of light and inhibited by darkness. To determine its role in ME, we created OsPAO5 mutants using CRISPR/Cas9. Compared with the wild type, pao5 mutants had longer mesocotyls, released less H 2 O 2 , and synthesized more ethylene. The mutant seedlings emerged at a higher and more uniform rate, indicating their potential for use in direct seeding. Nucleotide polymorphism analysis revealed that an SNP (PAO5 À578G/A ) located 578 bp upstream of the OsPAO5 start codon alters its expression, and was selected during rice mesocotyl domestication. The PAO5 À578G genotype conferring a long mesocotyl mainly exists in wild rice, most Aus accessions, and some Geng (Japonica) accessions. Intriguingly, knocking out OsPAO5 can remarkably increase the grain weight, grain number, and yield potential. In summary, we developed a novel strategy to obtain elite rice with higher emergence vigor and yield potential, which can be conveniently and widely used to breed varieties of direct-seeding rice.

Polyamine Metabolism under Different Light Regimes in Wheat

“…Most of these experiments were carried out in growth chambers with photosynthetic photon flux density (PPFD) in the range of 100-270 μmol m 2 s −1 with one day/night regime [8][9][10][11]13,14,22,29,32,34,36]; some of them were conducted under higher light conditions [30,31,41] and none of them under different hours of illumination. In addition, only a few studies are available on the comparison of changes in dedicated components of the PA metabolism under different light conditions [21][22][23][24][25][26], and none of them reported the simultaneous effect of exogenous PA treatments. Therefore, in the present study, our aim was the better understanding of the effect of light on PA metabolism and how the exogenous PA treatments may modify the interaction of PAs and light.…”

“…Light controls PA biosynthesis [20]. The changes in the activity of both PA synthesis enzymes-arginine decarboxylase (ADC), ornithine decarboxylase (ODC), spermidine synthase (SPDS), spermine synthase [21][22][23]-and catabolite enzymes-polyamine oxidase (PAO) [22,24,25], or TGase-have been reported in the presence of different light conditions [24,26]. It has also been proven that PAs are able to influence photosynthesis at several levels: for example, they can modify the chlorophyll destruction and/or biosynthesis; binding to photosynthetic complexes can induce conformal changes; as buffer compounds in the thylakoid lumen, they may increase chemiosmotic ATP synthesis [27].…”

Integrative QTL Identification, Fine Mapping and Candidate Gene Analysis of a Major Locus qLTG3a for Seed Low-Temperature Germinability in Rice

“…Low temperatures limit the geographical distribution and planting time of crops, thus affecting food production. Reduced freshwater resources and increasing labor costs have driven the rise of direct-seeded rice in China and worldwide (Lv et al 2020 ; Mahender et al 2015 ). Genetic improvement of LTG for current rice varieties is a crucial strategy to ensure direct-seeded rice success.…”

Rapid Identification of QTL for Mesocotyl Length in Rice Through Combining QTL-seq and Genome-Wide Association Analysis

“…A candidate gene with identical SNPs or InDels in the male parent of the co-localized population was further selected. As mesocotyl elongation is highly regulated by various phytohormones, including strigolactones (SLs), cytokinins (CTKs), brassinosteroids (BRs), abscisic acid (ABA), jasmonates (JAs), gibberellins (GAs), and auxins (IAAs) ( Watanabe and Takahashi, 1999 ; Cao et al, 2005 ; Hu et al, 2014 ; Xiong et al, 2017 ; Sun et al, 2018 ; Zheng et al, 2020 ; Lv et al, 2021 ), those genes involved in phytohormone metabolism were regarded as high-confidence candidate genes for mesocotyl elongation.…”

“…Up to now, over 40 quantitative trait loci (QTL) on 12 rice chromosomes have been identified, which could explain 5.7–27.8% of the phenotypic variation ( Cao et al, 2002 ; Liu et al, 2020 ; Rohilla et al, 2020 ; Zhan et al, 2020 ). Four genes were cloned: OsGY1 ( Xiong et al, 2017 ), OsGSK2 ( Sun et al, 2018 ), OsSMAX1 ( Zheng et al, 2020 ), and OsPAO5 ( Lv et al, 2021 ). Recently, genome-wide association study (GWAS) based on linkage disequilibrium (LD) has been widely applied to identify marker–trait associations (MTAs) for complex agronomic traits ( Meng et al, 2016 ; Zhan et al, 2020 ; Liu et al, 2021 ).…”