Search

Magnaporthe oryzae caused huge losses in rice and wheat production worldwide. Comparing to long-term co-evolution history with rice, wheat-infecting isolates were new-emerging. To reveal the genetic differences between rice and wheat blast on global genomic scale, 109 whole-genome sequences of M. oryzae from rice, wheat, and other hosts were reanalyzed in this study. We found that the rice lineage had gone through stronger selective sweep and fewer conserved genes than those of Triticum and Lolium lineages, which indicated that rice blast fungi adapted to rice by gene loss and rapid evolution of specific loci. Furthermore, 228 genes associated with host adaptation of M. oryzae were found by presence/absence variation (PAV) analyses. The functional annotation of these genes found that the fine turning of genes gain/loss involved with transport and transcription factor, thiol metabolism, and nucleotide metabolism respectively are major mechanisms for rice adaption. This result implies that genetic base of specific host plant may lead to gene gain/loss variation of pathogens, so as to enhance their adaptability to host. Further characterization of these specific loci and their roles in adaption and evaluation of the fungi may eventually lead to understanding of interaction mechanism and develop new strategies of the disease management.

In the field, the chemical constituents of the essential oil of Pelargonium graveolens cutting (diploid) and polyploid seedlings are the same, but the principal components of geraniol, geranyl formate, and linalool in polyploid plants are remarkably higher than those of cutting seedlings. The contents of citronellol, citronellyl formate, and rose oxide are significantly lower in polyploid seedlings than in cutting seedlings. ISSR and RAPD molecular markers were used to analyze P. graveolens in two different genetic populations and to compare the genetic background of differences between cutting and polyploid seedlings. The genomic DNA of 60 cutting and polyploid seedlings was extracted for PCR amplification by using 3 ISSR primers and 11 RAPD primers for random sampling from adjacent cultivated fields. Among the primers, ISSR-25 primer detected the highest diversity of the loci. Seven loci of variation were found in the two populations. The variation rates detected using 3 ISSR primers were 13.3% and 6.7% for the cutting and polyploid populations, respectively. Genetic polymorphisms in P. graveolens genome with mutation rates of 11.7% and 3.3% were respectively determined in cutting and polyploid seedlings by using 3 RAPD primers (B11, P4, and R19). Both types of molecular markers also revealed the mutation in cutting and polyploid seedlings. Results demonstrated that a genetic difference can be observed by the molecular markers, although no evident phenotypic difference exists in cutting and polyploid seedlings in fields. The trend of these molecular markers is consistent, that is, individual genetic differences in cutting seedlings are greater than those in polyploid seedlings. These results suggested that polyploid seedlings in a population are relative uniform and applicable to production.

Magnaporthe grisea is the causal agent of rice blast disease, which is the most serious disease of cultivated rice. Aromatic polyketides are its typical metabolites and are involved in the infection process. In the search for novel lead compounds, chemical investigation of the fungus M. grisea M639 has led to the isolation of four new aromatic polyketides (salicylaldehyde skeleton bearing an unsaturated side chain), griseaketides A&ndash, D (1&ndash, 4), as well as 15 known compounds (5&ndash, 19). The structures of the new compounds were elucidated on the basis of extensive spectroscopic analyses, including HR-MS, 2D NMR. Compound 12 showed prominent activity that killed 94.5% of C. elegans at 400 ppm and 66.9% at 200 ppm over 24 h. This is the first report describing the nematicidal activity of this type aromatic polyketide.

The embryo sac plays a vital role in sexual reproduction of angiosperms. LysM domain containing proteins with multiple lysin motifs are widespread proteins and are involved in plant defense responses against fungal chitins and bacterial peptidoglycans. Various studies have reported the role of LysM domain-containing proteins in plant defense mechanisms but their involvement in sexual reproduction remains largely unknown. Here, we report the involvement of a LysM domain-containing gene, EMBRYO SAC 1 (OsEMSA1), in the sexual reproduction of rice. The gene encoded a LysM domain-containing protein that was necessary for embryo sac development and function. The gene was expressed in root, stem, leaf tissues, panicle and ovaries and had some putative role in hormone regulation. Suppression of OsEMSA1 expression resulted in a defective embryo sac with poor differentiation of gametophytic cells, which consequently failed to attract pollen tubes and so reduced the panicle seed-setting rate. Our data offers new insight into the functions of LysM domain-containing proteins in rice.

The embryo sac plays a vital role in sexual reproduction of angiosperms. LysM domain containing proteins with multiple lysin motifs are widespread proteins and are involved in plant defense responses against fungal chitins and bacterial peptidoglycans. Various studies have reported the role of LysM domain-containing proteins in plant defense mechanisms but their involvement in sexual reproduction remains largely unknown. Here, we report the involvement of a LysM domain-containing gene, EMBRYO SAC 1 (OsEMSA1), in the sexual reproduction of rice. The gene encoded a LysM domain-containing protein that was necessary for embryo sac development and function. The gene was expressed in root, stem, leaf tissues, panicle and ovaries and had some putative role in hormone regulation. Suppression of OsEMSA1 expression resulted in a defective embryo sac with poor differentiation of gametophytic cells, which consequently failed to attract pollen tubes and so reduced the panicle seed-setting rate. Our data offers new insight into the functions of LysM domain-containing proteins in rice.

Using a small pilot coating pan, red clover and tall fescue seeds were coated under different rotating speed of pan (20, 30, 40, 45, 55, 60 rpm) for standardization of seed coating. Vermiculite was used as particulate matter and polyvinyl alcohol as adhesive for the coating of seeds. Coating index was calculated based on the percent singles out, percent agglomerates out, weight of particulate matter fine, percent friability, and average weight per 100 seeds to evaluate the physical characteristics of coated seeds. The coated seed of red clover under 45 rpm rotating speed of pan, was best in terms of percent singles out, percent agglomerates out, weight of fines, and average 100 seed weight. The coated seed of tall fescue under 40 rpm rotating speed of pan, showed highest percent singles out, lowest percent agglomerates out, lowest weight of fines, and heaviest average 100 seed weight. Excellent coating results were obtained with the pan speed of 45rpm for red clover and 40 rpm for tall fescue seeds. As rotatory speed of coating pan affected much to the physical characteristics of coated seeds, standardization of the speed is required before seed coating.(

Many homeotic MADS-box genes have been identified as controllers of the floral transition and floral development. However, information regarding Bsister (Bs)-function genes in monocots is still limited. Here, we describe the functional characterization of a Bs-group MADS-box gene FEMALE-STERILE (FST), whose frame-shift mutation (fst) results in abnormal ovules and the complete abortion of zygotic embryos and endosperms in rice. Anatomical analysis showed that the defective development in the fst mutant exclusively occurred in sporophytic tissues including integuments, fertilized proembryos and endosperms. Analyses of the spatio-temporal expression pattern revealed that the prominent FST gene products accumulated in the inner integument, nucellar cell of the micropylar side, apical and base of the proembryos and free endosperm nuclei. Microarray and gene ontology analysis unraveled substantial changes in the expression level of many genes in the fst mutant ovules and seeds, with a subset of genes involved in several developmental and hormonal pathways appearing to be down-regulated. Using both forward and reverse genetics approaches, we demonstrated that rice FST plays indispensable roles and multiple functions during ovule and early seed development. These findings support a novel function for the Bs-group MADS-box genes in plants.

Fagopyrum homotropicum Ohnishi is a self-pollinating wild buckwheat species indigenous to eastern Tibet and the Yunnan and Sichuan Provinces of China. It is useful breeding material for shifting cultivated buckwheat (F. esculentum ssp. esculentum Moench) from out-crossing to self-pollinating. Despite its importance as a genetic resource in buckwheat breeding, the genetic variation of F. homotropicum is poorly understood. In this study, we investigated the genetic variation and phylogenetic relationships of the diploid and tetraploid forms of F. homotropicum based on the nucleotide sequences of a nuclear gene, AGAMOUS (AG). Neighbor-joining analysis revealed that representative individuals clustered into three large groups (Group I, II and III). Each group contained diploid and tetraploid forms of F. homotropicum. We identified tetraploid plants that had two diverged AG sequences; one belonging to Group I and the other belonging to Group II, or one belonging to Group II and the other belonging to Group III. These results suggest that the tetraploid form originated from at least two hybridization events between deeply differentiated diploids. The results also imply that the genetic diversity contributed by tetraploidization of differentiated diploids may have allowed the distribution range of F. homotropicum to expand to the northern areas of China.

Co-inoculation of healthy standing rice plants with compatible isolates of Magnaporthe grisea pathogenic to rice resulted in the production of perithecia on the detached portions of leaf sheaths. The isolates had been obtained from the same lesion on a diseased plant collected in Yunnan Province, China. Peritheeia were also produced on dead tissue of leaf sheaths and nodes of standing rice plants in a moist chamber. These results strongly suggest that the teleomorph of M. grisea can occur in the upland rice fields in Yunnan.