The transition from the prostrate growth of ancestral wild rice (O. rufipogon Griff.) to the erect growth of Oryza sativa cultivars was one of the most critical events in rice domestication. This evolutionary step importantly improved plant architecture and increased grain yield. Here we find that prostrate growth of wild rice from Yuanjiang County in China is controlled by a semi-dominant gene, PROG1 (PROSTRATE GROWTH 1), on chromosome 7 that encodes a single Cys(2)-His(2) zinc-finger protein. prog1 variants identified in O. sativa disrupt the prog1 function and inactivate prog1 expression, leading to erect growth, greater grain number and higher grain yield in cultivated rice. Sequence comparison shows that 182 varieties of cultivated rice, including 87 indica and 95 japonica cultivars from 17 countries, carry identical mutations in the prog1 coding region that may have become fixed during rice domestication.

A critical evolutionary step during rice domestication was the elimination of seed shattering. Wild rice disperses seeds freely at maturity to guarantee the propagation, while cultivated rice retains seeds on the straws to make easy harvest and decrease the loss of production. The molecular basis for this key event during rice domestication remains to be elucidated. Here we show that the seed shattering is controlled by a single dominant gene, Shattering1 (SHA1), encoding a member of the trihelix family of plant-specific transcription factors. SHA1 was mapped to a 5.5 kb genomic fragment, which contains a single open reading frame, using a backcrossed population between cultivated rice Teqing and an introgression line IL105 with the seed shattering habit derived from perennial common wild rice, YJCWR. The predicted amino acid sequence of SHA1 in YJCWR and IL105 is distinguished from that in eight domesticated rice cultivars, including Teqing, by only a single amino acid substitution (K79N) caused by a single nucleotide change (g237t). Further sequence verification on the g237t mutation site revealed that the g237t mutation is present in all the domesticated rice cultivars, including 92 indica and 108 japonica cultivars, but not in any of the 24 wild rice accessions examined. Our results demonstrate that the g237t mutation in SHA1 accounts for the elimination of seed shattering, and that all the domesticated rice cultivars harbor the mutant sha1 gene and therefore have lost the ability to shed their seeds at maturity. In addition, our data support the theory that the non-shattering trait selection during rice domestication occurred prior to the indica-japonica differentiation in rice evolutionary history.

Common wild rice (Oryza rufipogon), the wild relative of Asian cultivated rice (Oryza sativa), flaunts long, barbed awns, which are necessary for efficient propagation and dissemination of seeds. By contrast, O. sativa cultivars have been selected to be awnless or to harbor short, barbless awns, which facilitate seed processing and storage. The transition from long, barbed awns to short, barbless awns was a crucial event in rice domestication. Here, we show that the presence of long, barbed awns in wild rice is controlled by a major gene on chromosome 4, LONG AND BARBED AWN1 (LABA1), which encodes a cytokinin-activating enzyme. A frame-shift deletion in LABA1 of cultivated rice reduces the cytokinin concentration in awn primordia, disrupting barb formation and awn elongation. Sequencing analysis demonstrated low nucleotide diversity and a selective sweep encompassing an ;800-kb region around the derived laba1 allele in cultivated rice. Haplotype analysis revealed that the laba1 allele originated in the japonica subspecies and moved into the indica gene pool via introgression, suggesting that humans selected for this locus in early rice domestication. Identification of LABA1 provides new insights into rice domestication and also sheds light on the molecular mechanism underlying awn development.

In present study, Fe, Zn, Mn, Cu, Ca, Mg, P and K contents of 85 introgression lines (ILs) derived from a cross between an elite indica cultivar Teqing and the wild rice (Oryza rufipogon) were measured by inductively coupled argon plasma (ICAP) spectrometry. Substantial variation was observed for all traits and most of the mineral elements were significantly positive correlated or independent except for Fe with Cu. A total of 31 putative quantitative trait loci (QTLs) were detected for these eight mineral elements by single point analysis. Wild rice (O. rufipogon) contributed favorable alleles for most of the QTLs (26 QTLs), and chromosomes 1, 9 and 12 exhibited 14 QTLs (45%) for these traits. One major effect of QTL for zinc content accounted for the largest proportion of phenotypic variation (11%-19%) was detected near the simple sequence repeats marker RM152 on chromosome 8. The co-locations of QTLs for some mineral elements observed in this mapping population suggested the relationship was at a molecular level among these traits and could be helpful for simultaneous improvement of these traits in rice grain by marker assisted selection.

Inflorescence architecture is a key agronomical factor determining grain yield, and thus has been a major target of cereal crop domestication. Transition from a spread panicle typical of ancestral wild rice (Oryza rufipogon Griff.) to the compact panicle of present cultivars (O. sativa L.) was a crucial event in rice domestication. Here we show that the spread panicle architecture of wild rice is controlled by a dominant gene, OsLG1, a previously reported SBP-domain transcription factor that controls rice ligule development. Association analysis indicates that a single-nucleotide polymorphism-6 in the OsLG1 regulatory region led to a compact panicle architecture in cultivars during rice domestication. We speculate that the cis-regulatory mutation can fine-tune the spatial expression of the target gene, and that selection of cis-regulatory mutations might be an efficient strategy for crop domestication.

Cultivated rice (Oryza sativa) was domesticated from wild rice (Oryza rufipogon), which typically displays fewer grains per panicle and longer grains than cultivated rice. In addition, wild rice has long awns, whereas cultivated rice has short awns or lacks them altogether. These changes represent critical events in rice domestication. Here, we identified a major gene, GRAIN NUMBER, GRAIN LENGTH AND AWN DEVELOPMENT1 (GAD1), that regulates those critical changes during rice domestication. GAD1 is located on chromosome 8 and is predicted to encode a small secretary signal peptide belonging to the EPIDERMAL PATTERNING FACTOR-LIKE family. A frame-shift insertion in gad1 destroyed the conserved cysteine residues of the peptide, resulting in a loss of function, and causing the increased number of grains per panicle, shorter grains, and awnless phenotype characteristic of cultivated rice. Our findings provide a useful paradigm for revealing functions of peptide signal molecules in plant development and helps elucidate the molecular basis of rice domestication.

Grain size is an important yield-related trait in rice. Intensive artificial selection for grain size during domestication is evidenced by the larger grains of most of today's cultivars compared with their wild relatives. However, the molecular genetic control of rice grain size is still not well characterized. Here, we report the identification and cloning of Grain Size 6 (GS6), which plays an important role in reducing grain size in rice. A premature stop at the +348 position in the coding sequence (CDS) of GS6 increased grain width and weight significantly. Alignment of the CDS regions of GS6 in 90 rice materials revealed three GS6 alleles. Most japonica varieties (95%) harbor the Type I haplotype, and 62.9% of indica varieties harbor the Type II haplotype. Association analysis revealed that the Type I haplotype tends to increase the width and weight of grains more than either of the Type II or Type III haplotypes. Further investigation of genetic diversity and the evolutionary mechanisms of GS6 showed that the GS6 gene was strongly selected in japonica cultivars. In addition, a "ggc" repeat region identified in the region that encodes the GRAS domain of GS6 played an important historic role in the domestication of grain size in rice. Knowledge of the function of GS6 might aid efforts to elucidate the molecular mechanisms that control grain development and evolution in rice plants, and could facilitate the genetic improvement of rice yield.

During rice domestication and improvement, increasing grain yield to meet human needs was the primary objective. Rice grain yield is a quantitative trait determined by multiple genes, but the molecular basis for increased grain yield is still unclear. Here, we show that NUMBER OF GRAINS 1 (NOG1), which encodes an enoyl-CoA hydratase/isomerase, increases the grain yield of rice by enhancing grain number per panicle without a negative effect on the number of panicles per plant or grain weight. NOG1 can significantly increase the grain yield of commercial high-yield varieties: introduction of NOG1 increases the grain yield by 25.8% in the NOG1-deficient rice cultivar Zhonghua 17, and overexpression of NOG1 can further increase the grain yield by 19.5% in the NOG1-containing variety Teqing. Interestingly, NOG1 plays a prominent role in increasing grain number, but does not change heading date or seed-setting rate. Our findings suggest that NOG1 could be used to increase rice production.