Creation of male‐sterile lines that can be restored to fertility by exogenous methyl jasmonate for the establishment of a two‐line system for the hybrid production of rice (Oryza sativa L.)

Abstract

Male sterility is widely used in the production of hybrid seeds in rice, but the use of genic male sterility is limited because of the high labour cost for maintaining male‐sterile lines. Previous studies using T‐DNA insertional mutagenesis demonstrated that disrupting the expression of oxophytodienoic acid reductase 3 (OPR3), which is involved in the jasmonate biosynthesis pathway, results in a kind of male sterility that can be restored to fertility by exogenous jasmonate in Arabidopsis. Here, we created male‐sterile mutations by editing the second and fourth exons of OsOPR7 in rice through clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR‐associated system 9. The induced mutagenesis at these exons resulted in 31.8% and 23.9% male‐sterile plants in the T0 generation, respectively. We screened male‐sterile lines that can be restored to fertility by exogenous methyl jasmonate in the T0, T1 and T2 rice populations and characterized the anther and agronomic traits of the transgenic plants. Results showed the successful generation of male‐sterile lines through the silencing of OsOPR7, the orthologous gene of Arabidopsis OPR3, in a field crop, paving the way for the establishment of a two‐line system for rice hybrid production. The system consists of a male‐sterile line that can be maintained by spraying methyl jasmonate and a restoring line that confers pollen.

Jasmonic Acid Plays a Pivotal Role in Pollen Development and Fertility Regulation in Different Types of P(T)GMS Rice Lines

“…Subsequently, a number of candidate genes related to fertility were reported in PTGMS rice, such as tms 1, tms 2, ptgms 2-1, and p/tms 12-1, located on chromosome 11 [ 9 , 10 , 11 , 12 , 13 ]. A great deal of information related to genic male sterility has been revealed through reverse genetics, such as the identification of cytochrome P450 members ( OsCYP703A3 and OsCYP704B2 ), fatty acyl-CoA synthetase ( OsACOS12 ), polyketide synthases ( OsPKS1/2 ), ATP binding cassette G transporters ( OsABCG15/26 ), lipid transporter genes ( OsC6 ) and 12-oxophytodeinoate reductase ( Os OPR7 ) involved in lipid synthesis [ 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ]. The pollen exine has a multi-layered structure, and the main component is sporopollenin.…”

The OPR gene family in watermelon: Genome‐wide identification and expression profiling under hormone treatments and root‐knot nematode infection

“…ClOPR4 along with AtOPR1 and AtOPR2 were clustered in OPRI, and ClOPR2 was clustered in OPRII (Fig. 2A), which is the group with AtOPR3 (Schaller et al 2000), OsOPR7 (Tani et al 2008; Pak et al 2020), ZmOPR7 and ZmOPR8 (Yan et al 2012). Therefore, it can be speculated that ClOPR2 and ClOPR4 might participate in defence responses, as in other plants (Berni et al 2019; Mou et al 2019).…”

“…Jasmonates, a family of chemical compounds derived from jasmonic acid (JA), are recognized phytohormones that play key roles in plant defence against herbivores, root-knot nematodes (RKN), necrotrophic pathogens and various abiotic stressors (Nahar et al 2011;Per et al 2018;Wasternack & Stnad 2006). Furthermore, JA and its related octadecanoid can act as signals to mediate plant growth and development processes, such as stamen development, flowering time, fruit ripening, seed germination and senescence (Wasternack & Song 2016;Ruan et al 2019).…”

“…In addition, AtOPR3 explicitly inhibits primary root growth under phosphate deficiency in Arabidopsis (Zheng et al 2016), and overexpression of AtOPR3 in bread wheat leads to elevated JA content and alters plant development, including germination, growth, late flowering and senescence, and improves tolerance to short‐term freezing (Pigolev et al 2018). In rice, OsOPR7 is required for JA biosynthesis, and CRISPR/Cas9‐induced osopr7 mutants exhibit a male‐sterile phenotype with reduced levels of endogenous JA, and their fertility can be restored with exogenous methyl jasmonate (MeJA) (Tani et al 2008; You et al 2019; Pak et al 2020). In maize, the JA content of all organs in the double mutant opr7opr8 was dramatically reduced, leading to substantial developmental defects and extreme susceptibility to pathogens and insects (Yan et al 2012).…”

Exploiting Genic Male Sterility in Rice: From Molecular Dissection to Breeding Applications

“…osopr7 mutants created using CRISPR/Cas9 displayed anther indehiscence and complete male sterility. The exogenous application of methyl jasmonate (MeJA) makes it possible to restore fertility and facilitates seed setting through the selfing of mutant plants (Pak et al, 2020). The seeds can then be used for the propagation of male sterile lines and hybrid production by crossing the male sterile lines with desirable fertile lines (Figure 7).…”