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The evening complex (EC) plays a critical role in photoperiod flowering in Arabidopsis. Nevertheless, the underlying functions of individual components and coordinate regulation mechanism of EC genes in rice flowering remain to be elucidated. Here, we characterized the critical role of LUX ARRHYTHMO (LUX) in photoperiod perception and coordinating vegetative growth and flowering in rice. Non-functional alleles of OsLUX extremely extended vegetative phase, leading to photoperiod-insensitive late flowering and great increase of grain yield. OsLUX displayed an obvious diurnal rhythm expression with the peak at dusk and promoted rice flowering via coordinating the expression of genes associated with the circadian clock and the output integrators of photoperiodic flowering. OsLUX combined with OsELF4a and OsELF3a or OsELF3b to form two ECs, of which the OsLUX-OsELF3a-OsELF4a was likely the dominant promoter for photoperiodic flowering. In addition, OsELF4a was also essential for promoting rice flowering. Unlike OsLUX , loss OsELF4a displayed a marginal influence under short-day (SD) condition, but markedly delayed flowering time under long-day (LD) condition. These results suggest that rice EC genes share the function of promoting flowering. This is agreement with the orthologs of SD plant, but opposite to the counterparts of LD species. Taken together, rice EC genes display similar but not identical function in photoperiodic flowering, probably through regulating gene expression cooperative and independent. These findings facilitate our understanding of photoperiodic flowering in plants, especially the SD crops. [ABSTRACT FROM AUTHOR]

OsMADS16, a class B floral organ identity gene, plays a pivotal role in stamen formation in rice. To date, little is known about the interacting partners of OsMADS16 except for several MADS-box proteins. In this study, we constructed a high-quality cDNA library of young panicles (< 5 cm in length) and performed yeast two-hybrid (Y2H) screening using OsMADS16 as bait. Eleven candidate proteins interacting with OsMADS16 were identified by Y2H and validated by BiFC and Co-IP assays. Subcellular localization results further confirmed the possibility of the interactions of OsMADS16 with 10 of the candidate proteins in natural rice cells. Bioinformatics analysis indicated that these partners exerted various molecular, cellular and physiological functions. Some of them were known or likely to be related to reproductive events, such as stamen primordium initiation, differentiation and development (OsMADS2, OsMADS4 and OsCOP9) and pollen development (OsbHLH40 and Os6PGDH). Our results provide an important reference for further research on OsMADS16-mediated regulation mechanism on floral organ development and pollen formation. [ABSTRACT FROM AUTHOR]

Tobacco bacterial wilt (TBW) is one of the most serious tobacco diseases in the world. Studies have shown that tobacco resistance to TBW is quantitatively inherited. This study aimed to map quantitative trait loci (QTL) conferring TBW resistance. An F2 : 3 population containing 237 lines was developed from a cross between two flue-cured tobacco cultivars, 'Yanyan 97' (YY97; moderately resistant to TBW) and 'Honghua Dajinyuan' (HD; highly susceptible to TBW), and a linkage map consisting of 201 simple sequence repeats (SSR) markers and spanning a total length of 2326.7 cM was constructed based on the population. Field experiments were conducted 2011 and 2012, and disease symptoms were investigated three times in each year. The phenotypic data were analysed either separately or jointly for QTL mapping using the software QTLNetwork 2.1. Eight QTL with significant main effects were mapped on chromosomes 2, 6, 12, 17 and 24. A major QTL ( qBWR17a) was detected on chromosome 17, which explained up to 30% of the phenotypic variation. The results can facilitate marker-assisted selection (MAS) in TBW resistance breeding programme. [ABSTRACT FROM AUTHOR]

Bacterial leaf steak (BLS) is one of the most destructive diseases in rice. Studies have shown that BLS resistance in rice is quantitatively inherited, controlled by multiple quantitative trait loci (QTLs). A QTL with relatively large effect, qBlsr5a, was previously mapped in a region of ∼380 kb on chromosome 5. To fine map qBlsr5a further, a set of overlapping sub-chromosome segment substitution lines (sub-CSSLs) were developed from a large secondary F2 population (containing more than 7000 plants), in which only the chromosomal region harboring qBlsr5a was segregated. By genotyping the sub-CSSLs with molecular markers covering the target region and phenotyping the sub-CSSLs with artificial inoculation, qBlsr5a was delimited to a 30.0-kb interval, in which only three genes were predicted. qRT-PCR analysis indicated that the three putative genes did not show significant response to the infection of BLS pathogen in both resistant and susceptible parental lines. However, two nucleotide substitutions were found in the coding sequence of gene LOC_Os05g01710, which encodes the gamma chain of transcription initiation factor IIA (TFIIAγ). The nucleotide substitutions resulted in a change of the 39th amino acid from valine (in the susceptible parent) to glutamic acid (in the resistant parent). Interestingly, the resistant parent allele of LOC_Os05g01710 is identical to xa5, a major gene resistant to bacterial leaf blight (another bacterial disease of rice). These results suggest that LOC_Os05g01710 is very possibly the candidate gene of qBlsr5a. [ABSTRACT FROM AUTHOR]

Recent studies have shown that F-box proteins constitute a large family in eukaryotes, and play pivotal roles in regulating various developmental processes in plants. However, their functions in monocots are still obscure. In this study, we characterized a recessive mutant dwarf and deformed flower 1-1 ( ddf1-1) in Oryza sativa (rice). The mutant is abnormal in both vegetative and reproductive development, with significant size reduction in all organs except the spikelet. DDF1 controls organ size by regulating both cell division and cell expansion. In the ddf1-1 spikelet, the specification of floral organs in whorls 2 and 3 is altered, with most lodicules and stamens being transformed into glume-like organs and pistil-like organs, respectively, but the specification of lemma/palea and pistil in whorls 1 and 4 is not affected. DDF1 encodes an F-box protein anchored in the nucleolus, and is expressed in almost all vegetative and reproductive tissues. Consistent with the mutant floral phenotype, DDF1 positively regulates B-class genes OsMADS4 and OsMADS16, and negatively regulates pistil specification gene DL. In addition, DDF1 also negatively regulates the Arabidopsis LFY ortholog APO2, implying a functional connection between DDF1 and APO2. Collectively, these results revealed that DDF1, as a newly identified F-box gene, is a crucial genetic factor with pleiotropic functions for both vegetative growth and floral organ specification in rice. These findings provide additional insights into the molecular mechanism controlling monocot vegetative and reproductive development. [ABSTRACT FROM AUTHOR]

Med8, a subunit of mediator complex, has proved to possess crucial functions in many organisms from yeast to human. In plant, the med8 mutant of Arabidopsis thaliana displayed delayed anthesis and increased number of leaves during the vegetative period. However, the roles of Med8 in other flowering plants are still unknown. To investigate the function of Med8 ortholog in tobacco ( Nicotiana tabacum L.; named as Nt Med8), we created transgenic tobacco plants with repressed Nt Med8 expression mediated by RNA interference (RNAi). Compared with the wild type, the Nt Med8-RNAi plants exhibited: more leaves with smaller but thicker blades; larger cells and vascular bundles with lower stomata density in leaves; swelled chloroplasts with thicker and lumen-enlarged thylakoids; weaker root system with fewer lateral roots; larger flowers and floral organs; flowering earlier under long day, but later under short day conditions; and male sterile with larger but less germinable pollens. In addition, quantitative RT-PCR indicated that Nt Med8 is expressed in both vegetative and floral tissues. Subcellular localization analysis by transient expression of fusion protein in Nicotiana benthamiana leaves showed that NtMed8 was located in both plasma membrane and nucleus. These results suggest that Nt Med8 plays important roles in both vegetative and reproductive development, and the function of Med8 appears to be, at least partially, conserved in flowering plants. [ABSTRACT FROM AUTHOR]

In this article, we report an independent work of positional cloning and functional characterization of Os JAG gene in rice. The merit of our work is that we used a genuine null mutant, in which the wild-type allele was completely deleted. This allowed us to identify the mutant phenotypes accurately without the interference of residual function of the target gene. Os JAG is an important gene with pleiotropy, expressing almost throughout the plant and acting in both vegetative phase and reproductive phase. But its main and crucial roles are in regulating the development of all floral organs, especially in specifying the identity of stamens. Interestingly, Os JAG does not affect the number of floral organ primordial and so of floral organs in each whorl, suggesting that Os JAG does not influence the initiation of floral organ primordia, but affect the developmental fate of all floral organs after their primordia have initiated. Loss of Os JAG function results in maldevelopment of all floral organs, such as degenerated lemma and palea, elongated lodicules and deformed and sterile pistil. The stamen appears to be more sensitive to the mutation. All the six stamens in a mutant floret were thoroughly transformed into six pistil-like organs developed at the presumptive positions of the stamens in whorl 3. [ABSTRACT FROM AUTHOR]

Presents the genetic analysis and gene mapping of leafy head, a mutant blocking the differentiation of rachis branches in rice. Characteristics of the mutant; Influence of the genetic background on the mutant phenotype; Positional cloning and functional study of the mutant gene.

A mutant of spikelet differentiation in rice called frizzle panicle (fzp) was discovered in the progeny of a cross between Oryza sativa ssp. indica cv. V20B and cv. Hua1B. The mutant exhibits normal plant morphology but has apparently fewer tillers. The most striking change in fzp is that its spikelet differentiation is completely blocked, with unlimited subsequent rachis branches generated from the positions where spikelets normally develop in wild-type plants. Genetic analysis suggests that fzp is controlled by a single recessive gene, which is temporarily named fzp( t). Based on its mutant phenotype, fzp( t) represents a key gene controlling spikelet differentiation. Some F2 mutant plants derived from various genetic background appeared as the “middle type”, suggesting that the action of fzp( t) is influenced by the presence of redundant, modifier or interactive genes. By using simple sequence repeat (SSR) markers and bulked segregant analysis (BSA) method, fzp(t) gene was mapped in the terminal region of the long arm of chromosome 7, with RM172 and RM248 on one side, 3.2 cM and 6.4 cM from fzp(t), and RM18 and RM234 on the other side, 23.1 cM and 26.3 cM from fzp(t), respectively. These results will facilitate the positional cloning and function studies of the gene. [ABSTRACT FROM AUTHOR]