Mutation in CSA creates a new photoperiod-sensitive genic male sterile line applicable for hybrid rice seed production

Abstract

Rice is a major staple food worldwide. Making hybrid rice has proved to be an effective strategy to significantly increase grain yield. Current hybrid rice technologies rely on male sterile lines and have been used predominantly in indica cultivars. However, intrinsic problems exist in the implementation of these technologies, such as limited germplasms and unpredictable conversions from sterility to fertility in the field. Here, we describe a photoperiod-controlled male sterile line, carbon starved anther (csa), which contains a mutation in an R2R3 MYB transcription regulator of pollen development. This mutation was introduced into indica and japonica rice, and it rendered male sterility under short-day conditions and male fertility under long-day conditions in both lines. Furthermore, F 1 plants of csa and a restorer line JP69 exhibited heterosis (hybrid vigor), suggesting the feasibility of using this mutation to create hybrid rice. The csabased photoperiod-sensitive male sterile line allows the establishment of a stable two-line hybrid system, which promises to have a significant impact on agriculture.PGMS line | hybrid breeding | sugar partitioning R ice (Oryza sativa L.) is a major staple food that feeds more than one-half of the human population (1). The three-and two-line hybrid rice breeding technologies take advantage of heterosis (hybrid vigor) and have been successfully applied in many countries, leading to a more than 20% yield increase over inbred varieties (2). The three-line hybrid rice breeding system was developed in the 1970s after the revolutionary discovery of the wild abortive cytoplasmic male sterile cytoplasm (CMS-WA) for the breeding of CMS lines, which solved the problem of selfpollination in the varieties used for hybrid rice production (3). In this technology, a restorer line that contains the restorer gene(s) is used as the pollen donor to recover male fertility in F 1 plants (hybrid rice) after its cross with the CMS line (Fig. S1A). To maintain CMS, a maintainer line, which has viable pollen grains and normal seed sets, is used as the pollinator to cross with the CMS line (Fig. S1A). Although this system has been widely used for hybrid rice seed production, the requirement of a maintainer line with normal cytoplasm and a restorer line with nuclearencoded fertility restorer genes restricts breeders from exploiting more rice germplasms and complicates the procedures for generating hybrid seeds (4).As a replacement of the three-line technology, a two-line system has been developed and applied for hybrid rice seed production after the discovery of the environmentally sensitive genic male sterile lines controlled by nuclear recessive gene(s). A japonica cultivar, Nongken 58S (NK58S), was the first spontaneous photoperiod-sensitive genic male sterile (PGMS) mutant identified (5). Because indica varieties are predominant in most rice planting regions, the PGMS loci/locus in NK58S were/was introduced into indica to generate breeding cultivars, such as Peiai 64S (PA64S) and Xin'an S. These ...

iTRAQ-facilitated proteomic profiling of anthers from a photosensitive male sterile mutant and wild-type cotton (Gossypium hirsutum L.)

“…Interestingly, this mutation resulted in thermosensitive male sterility (TSMS) phenotype in indica cultivar Peiai64S (PA64S), suggesting that male fertility is controlled by cross-talk between the genetic networks and environmental conditions [15]. Ulike NK58S, the carbon starved anther (csa) mutant displays male sterility under short-day conditions but fertility under long-day conditions [2]. CSA, an R2R3 MYB transcription factor, took part in regulating sugar partitioning from leaves to anthers to promote pollen maturation by directly regulating the expression of OsMST8 [16].…”

“…Taking advantage of PSMS lines could greatly simplify breeding and seed production procedures, and easily match the restorer lines in hybrid breeding system [2,12]. The mechanism of PSMS has been well illustrated in rice using PSMS mutants.…”

“…However, the current cotton hybrid seeds are mainly produced through hand emasculation and pollination, which requires a large labor force and cost. As an alternative, male sterile lines are used as the female parent in the hybrid breeding system to simplify the breeding procedure [2].…”

COLLAPSED ABNORMAL POLLEN1Gene Encoding the Arabinokinase-Like Protein Is Involved in Pollen Development in Rice

“…Mutant analyses of defective tapetums have revealed several genes critical for pollen development, such as the gibberellin-regulated R2R3 MYB transcription factor GAMYB; the C2-GRAM domain protein gene ORYZA SATIVA NO POLLEN; UNDEVELOPED TAPETUM1, which encodes a basic helix-loop-helix transcription factor; WAX-DEFICIENT ANTHER1, encoding an enzyme involved in the synthesis of very-long-chain fatty acids; basic helix-loophelix protein genes TAPETUM DEGENERATION RETARDATION and ETERNAL TAPETUM1 (EAT1); UDP GLC PYROPHOSPHORYLASE1 (UGP1); the lipid transfer protein gene named OsC6; the R2R3 MYB transcription factor CARBON STARVED ANTHER (CSA); a cytochrome P450 family gene, CYP704B2; a C-class MADS box gene, MADS3; APOPTOSIS INHIBITOR5 (API5); and MICROSPORE AND TAPETUM REGU-LATOR1. In these mutants, cells within anthers began to degenerate at the meiosis or microspore stages, eventually resulting in no pollen or complete pollen collapse (Kaneko et al, 2004;Jiang et al, 2005;Jung et al, 2005Jung et al, , 2006Li et al, 2006Li et al, , 2010aLi et al, , 2011Chen et al, 2007;Chhun et al, 2007;Aya et al, 2009;Zhang et al, 2010aZhang et al, , 2010bZhang et al, , 2013Hu et al, 2011;Tan et al, 2012;Niu et al, 2013).…”

RNase ZS1 processes UbL40 mRNAs and controls thermosensitive genic male sterility in rice

“…Rice is strictly selfpollinating; therefore, hybrid varieties are bred using male-sterile maternal lines that fail to produce viable pollen, thus preventing self-pollination. Hybrid rice breeding uses the well-developed three-line and two-line systems 4,5 . The three-line system uses a cytoplasmic male-sterile (CMS) line, a restorer line and a CMS maintainer line to produce F 1 hybrid seeds and maintain the CMS line [6][7][8] .…”