The structure of the aerial part of a plant, referred to as plant architecture, is subject to strict genetic control, and grain production in cereal crops is governed by an array of agronomic traits. Rice is one of the most important cereal crops and is also a model plant for molecular biological research. Recently, significant progress has been made in isolating and collecting rice mutants that exhibit altered plant architecture. In this article we summarize the recent progress in understanding the basic patterning mechanisms involved in the regulation of tillering (branching) pattern, stem structure and leaf arrangement in rice plants. We discuss the relationship between the genetic modification of plant architecture and the improvement of pivotal agronomic traits in rice.

The domestication of crop plants has often involved an increase in apical dominance (the concentration of resources in the main stem of the plant and a corresponding suppression of axillary branches). A striking example of this phenomenon is seen in maize (Zea mays spp. mays), which exhibits a profound increase in apical dominance compared with its probable wild ancestor, teosinte (Zea mays ssp. parviglumis). Previous research has identified the teosinte branched1 (tb1) gene as a major contributor to this evolutionary change in maize. We have cloned tb1 by transposon tagging and show here that it encodes a protein with homology to the cycloidea gene of snapdragon. The pattern of tb1 expression and the morphology of tb1 mutant plants suggest that tb1 acts both to repress the growth of axillary organs and to enable the formation of female inflorescences. The maize allele of tb1 is expressed at twice the level of the teosinte allele, suggesting that gene regulatory changes underlie the evolutionary divergence of maize from teosinte.

In rice, many dwarf mutants have been isolated and characterized. We have investigated the relationship between dwarfism and the gibberellin (GA)-mediated control of physiological processes. Twenty-three rice cultivars and mutants (9 normal, 3 semi-dwarf, 11 dwarf) were analyzed in terms of two GA-mediated processes, namely, elongation of shoots and production of α-amylase activity in the endosperm. As a result, we identified four different groups (groups N, T, D and E). Two-dimensional plotting of the extent of induction of α-amylase in the endosperm versus the extent of enhancement of shoot elongation upon treatment with exogenous gibberellic acid (GA3) provided a useful method for the rapid allocation of large numbers of dwarf mutants of rice to the various groups. Members of group N (normal type), which included all normal cultivars and semi-dwarf mutants, showed a slight increase in elongation of shoots and a remarkable increase in production of α-amylase with the application of GA3 during germination. All of the dwarf mutants were classified as being members of the other three groups. Members of group T (Tan-ginbozu type), including three dwarf mutants, were highly responsive to exogenous GA3 in terms of elongation of shoots and production of α-amylase, with associated lower levels of endogenous GA. In contrast, members of the other three groups, including group N, had normal levels of endogenous GAs. Members of group D (Daikoku type) were only slightly responsive to exogenous GA3, an indication that they are GA-insensitive mutants. Members of group E (Ebisu type) had responses to GA3 similar to those of group N, not only in terms of elongation of shoots but also in terms of α-amylase production, an indication that they are dwarf mutants that can be considered as neither GA-deficient nor GA-insensitive mutants. We also examined a GA-insensitive mutant selected from among 19 near-isogenic dwarf lines of 'Shiokari', and we concluded that the d-1 gene is associated with the phenotype of GA-insensitive dwarf mutants.

Gibberellin (GA) regulates growth and development in plants. We isolated and characterized a rice GA-insensitive dwarf mutant, gid2. The GID2 gene encodes a putative F-box protein, which interacted with the rice Skp1 homolog in a yeast two-hybrid assay. In gid2, a repressor for GA signaling, SLR1, was highly accumulated in a phosphorylated form and GA increased its concentration, whereas SLR1 was rapidly degraded by GA through ubiquitination in the wild type. We conclude that GID2 is a positive regulator of GA signaling and that regulated degradation of SLR1 is initiated through GA-dependent phosphorylation and finalized by an SCF(GID2)-proteasome pathway.

Gibberellins (GAs) are phytohormones that are essential for many developmental processes in plants. It has been postulated that plants have both membrane-bound and soluble GA receptors; however, no GA receptors have yet been identified. Here we report the isolation and characterization of a new GA-insensitive dwarf mutant of rice, gid1. The GID1 gene encodes an unknown protein with similarity to the hormone-sensitive lipases, and we observed preferential localization of a GID1-green fluorescent protein (GFP) signal in nuclei. Recombinant glutathione S-transferase (GST)-GID1 had a high affinity only for biologically active GAs, whereas mutated GST-GID1 corresponding to three gid1 alleles had no GA-binding affinity. The dissociation constant for GA4 was estimated to be around 10(-7) M, enough to account for the GA dependency of shoot elongation. Moreover, GID1 bound to SLR1, a rice DELLA protein, in a GA-dependent manner in yeast cells. GID1 overexpression resulted in a GA-hypersensitive phenotype. Together, our results indicate that GID1 is a soluble receptor mediating GA signalling in rice.

The origin of agriculture led to the domestication of many plant species and to the exploitation of natural resources. It took almost 10,000 years for food grain production to reach 1 billion tons, in 1960, and only 40 years to reach 2 billion tons, in 2000. This unprecedented increase, which has been named the 'green revolution', resulted from the creation of genetically improved crop varieties, combined with the application of improved agronomic practices.

以9种遗传背景的矮败小麦近等基因系为材料，研究了矮秆不育株的株高、抽穗期、开花期、每株穗数、穗长、每穗小穗数和异交结实率。结果表明，不仅矮秆不育株与高秆可育株的株高存在显著差异，而且不同遗传背景的矮秆不育株的株高也程度不同的存在差异；矮秆不育株比高秆可育株的抽穗期平均晚2天，而开花期平均晚1天左右；在

PCR-based markers were developed to detect the point mutations responsible for the two major semi-dwarfing genes Rht-B1b ( Rht1) and Rht-D1b ( Rht2) in wheat. These markers were validated by testing 19 wheat varieties of known Rht genotype. They included Rht-B1b and Rht-D1b dwarfs, double-mutant varieties and tall wheats. These were correctly genotyped with the Rht-B1b and Rht-D1b-specific primers, as well as markers specific for the tall alleles Rht-B1a and Rht-D1a. Using a family of doubled-haploid lines segregating for Rht-B1b and Rht-D1b, the markers were mapped to the expected homoeologous regions of chromosomes 4B and 4D, respectively. Both markers were strongly correlated with a reduction in height, accounting for 23% ( Rht-B1b) and 44% ( Rht-D1b) of the phenotypic variance in the population. These markers will have utility in marker-assisted selection of the Rht-B1b and Rht-D1b genes in wheat breeding programs.

两年、两地的试验结果证明,Rht8半矮秆基因对地上部生物产量较Rht10和Rht12有显著的正向作用,并且生长发育较早,较接近目前推广种的生育时期,对不良环境有较强的适应性,利于产量性状的形成。Rht10的降秆作用最强,但由于节间缩短太多,造成地上部生物产量明显降低,使籽粒形成时提供营养的"源"太少,不利于高产。Rht12矮秆基因的降秆程度显著高于Rht8,但生物产量亦太低、成熟太晚和对环境条件的不适应,影响籽粒产量的提高,在以降秆为主要目标的育种中利用价值较大。

A dwarf mutant, dwarf 62 (d62), was isolated from rice cultivar 93-11 by mutagenesis with γ-rays. Under normal growth conditions, the mutant had multiple abnormal phenotypes, such as dwarfism, wide and dark-green leaf blades, reduced tiller numbers, late and asynchronous heading, short roots, partial male sterility, etc. Genetic analysis indicated that the abnormal phenotypes were controlled by the recessive mutation of a single nuclear gene. Using molecular markers, the D62 gene was fine mapped in 131-kb region at the short arm of chromosome 6. Positional cloning of D62 gene revealed that it was the same locus as DLT/OsGRAS-32, which encodes a member of the GRAS family. In previous studies, the DLT/OsGRAS-32 is confirmed to play positive roles in brassinosteroid (BR) signaling. Sequence analysis showed that the d62 carried a 2-bp deletion in ORF region of D62 gene which led to a loss-of-function mutation. The function of D62 gene was confirmed by complementation experiment. RT-PCR analysis and promoter activity analysis showed that the D62 gene expressed in all tested tissues including roots, stems, leaves and panicles of rice plant. The d62 mutant exhibited decreased activity of α-amylase in endosperm and reduced content of endogenous GA₁. The expression levels of gibberellin (GA) biosynthetic genes including OsCPS1, OsKS1, OsKO1, OsKAO, OsGA20ox2/SD1 and OsGA2ox3 were significantly increased in d62 mutant. Briefly, these results demonstrated that the D62 (DLT/OsGRAS-32) not only participated in the regulation of BR signaling, but also influenced GA metabolism in rice.

We generated a high-quality reference genome sequence for foxtail millet (Setaria italica). The similar to 400-Mb assembly covers similar to 80% of the genome and > 95% of the gene space. The assembly was anchored to a 992-locus genetic map and was annotated by comparison with > 1.3 million expressed sequence tag reads. We produced more than 580 million RNA-Seq reads to facilitate expression analyses. We also sequenced Setaria viridis, the ancestral wild relative of S. italica, and identified regions of differential single-nucleotide polymorphism density, distribution of transposable elements, small RNA content, chromosomal rearrangement and segregation distortion. The genus Setaria includes natural and cultivated species that demonstrate a wide capacity for adaptation. The genetic basis of this adaptation was investigated by comparing five sequenced grass genomes. We also used the diploid Setaria genome to evaluate the ongoing genome assembly of a related polyploid, switchgrass (Panicum virgatum).

Foxtail millet (Setaria italica), a member of the Poaceae grass family, is an important food and fodder crop in arid regions and has potential for use as a C-4 biofuel. It is a model system for other biofuel grasses, including switchgrass and pearl millet. We produced a draft genome (similar to 423 Mb) anchored onto nine chromosomes and annotated 38,801 genes. Key chromosome reshuffling events were detected through collinearity identification between foxtail millet, rice and sorghum including two reshuffling events fusing rice chromosomes 7 and 9, 3 and 10 to foxtail millet chromosomes 2 and 9, respectively, that occurred after the divergence of foxtail millet and rice, and a single reshuffling event fusing rice chromosome 5 and 12 to foxtail millet chromosome 3 that occurred after the divergence of millet and sorghum. Rearrangements in the C-4 photosynthesis pathway were also identified.