A novel male sterility-fertility restoration system in plants for hybrid seed production

Abstract

Hybrid seeds are used for stimulated crop production, as they harness heterosis. The achievement of complete male-sterility in the female-parent and the restored-fertility in F1-hybrids are the major bottlenecks in the commercial hybrid seed production. Here, we report a male sterility–fertility restoration system by engineering the inmost nutritive anther wall layer tapetum of female and male parents. In the female parent, high–level, and stringent expression of Arabidopsis autophagy–related gene BECLIN1 was achieved in the tapetum, which altered the tapetal degeneration program, leading to male sterility. This works on our previously demonstrated expression cassette based on functional complementation of TATA-box mutant (TGTA) promoter and TATA-binding protein mutant3 (TBPm3), with modification by conjugating Long Hypocotyle in Far-Red1 fragment (HFR1NT131) with TBPm3 (HFR1NT131-TBPm3) to exercise regulatory control over it. In the male parent, tapetum–specific Constitutive photo-morphogenesis1 (COP1) was expressed. The F1 obtained by crossing these engineered parents showed decreased BECLIN1 expression, which was further completely abolished when COP1-mutant (COP1L105A) was used as a male parent, leading to normal tapetal development and restored fertility. The system works on COP1-HFR1 interaction and COP1–mediated degradation of TBPm3 pool (HFR1NT131-TBPm3). The system can be deployed for hybrid seed production in agricultural crops.

Autophagy Mitigates High-Temperature Injury in Pollen Development of Arabidopsis thaliana

“…Autophagy plays a dispensable role in regular reproductive development, including tapetal PCD, in Arabidopsis, because almost all isolated autophagy-defective (atg) mutants can complete their life cycle under normal conditions (Yoshimoto 2012). Intriguingly, the occurrence of male sterility in a transgenic tobacco line overexpressing Arabidopsis AtATG6/BECLIN1 in the tapetum cells (Singh et al 2010(Singh et al , 2015 suggested that excessive autophagy might accelerate 3 tapetum cell death and lead to abortion of microsporogenesis in tobacco. Nevertheless, the rice autophagy null mutant OsATG7 showed a defect in tapetum cell degradation and sporophytic male sterility (Kurusu et al 2014;Hanamata et al 2014).…”

Interspecific cross‐hybrids of Nicotiana tabacum L. cv. (gla.) S ‘K326’ with Nicotiana alata

“…Therefore, precise control over pollen fertility in the female parent is practically needed, and several approaches have been explored (Singh et al. ). Cytoplasmic male sterility (CMS) is an effective method and has been exploited in hybrid breeding of some crop species (Touzet and Meyer , Islam et al ); yet, hybrids obtained through CMS line may be sterile, which restricts the economic benefits of the hybrid crops where the desired agricultural products are seeds (Singh et al.…”

“…Cytoplasmic male sterility (CMS) is an effective method and has been exploited in hybrid breeding of some crop species (Touzet and Meyer , Islam et al ); yet, hybrids obtained through CMS line may be sterile, which restricts the economic benefits of the hybrid crops where the desired agricultural products are seeds (Singh et al. ), or limits the sexual reproduction of these scarce hybrids. Consequently, it is extremely critical to exploit resources with fertility restoring gene and restore fertility in hybrid (Bentolila et al.…”

“…Emasculation is unavoidable when using a fertile maternal parent, and it is labour-intensive and time-consuming, and may occasionally result in pollen pollution. Therefore, precise control over pollen fertility in the female parent is practically needed, and several approaches have been explored (Singh et al 2015). Cytoplasmic male sterility (CMS) is an effective method and has been exploited in hybrid breeding of some crop species (Touzet andMeyer 2014, Islam et al 2014); yet, hybrids obtained through CMS line may be sterile, which restricts the economic benefits of the hybrid crops where the desired agricultural products are seeds (Singh et al 2015), or limits the sexual reproduction of these scarce hybrids.…”

“…Therefore, precise control over pollen fertility in the female parent is practically needed, and several approaches have been explored (Singh et al 2015). Cytoplasmic male sterility (CMS) is an effective method and has been exploited in hybrid breeding of some crop species (Touzet andMeyer 2014, Islam et al 2014); yet, hybrids obtained through CMS line may be sterile, which restricts the economic benefits of the hybrid crops where the desired agricultural products are seeds (Singh et al 2015), or limits the sexual reproduction of these scarce hybrids. Consequently, it is extremely critical to exploit resources with fertility restoring gene and restore fertility in hybrid (Bentolila et al 2002), and most of the fertility restoration genes encode pentatricopeptide repeat (PPR) containing proteins, which target the mitochondria or plastids for their function (Saha et al 2007).…”