||Rimi Yamaguchi, Koji Matsunaga, Tomonori Hirao, Miho Tamura, Atsushi Watanabe, Spatiotemporal analysis of pine wilt disease
Relationship between pinewood nematode distribution and defence response in Pinus thunbergii seedlings, Forest Pathology, 10.1111/efp.12518, 2019.01, Pine wilt disease is of major concern as it has destroyed pine forests in East Asia and Europe. Several studies have suggested that invasion by the pinewood nematode (PWN) Bursaphelenchus xylophilus, which causes this disease, evokes an excessive defence response in pine trees, resulting in tree death. However, few studies have quantitatively evaluated the correlation between PWN distribution and tree defence responses. Therefore, the present study aimed to quantify the number of PWNs and expression levels of putative pathogenesis-related (PR) genes in different positions of Japanese black pine (Pinus thunbergii) seedlings over time. To quantify the number of PWNs in the seedlings, we used TaqMan quantitative real-time PCR (qPCR) assay. During the early phase of infection, most PWNs were distributed around the inoculated sites, with only a small number being detected at distant sites, but the expression levels of PR genes were highly upregulated throughout the seedlings. Both the number of PWNs and expression levels of PR genes then increased drastically throughout the seedlings, all of which exhibited external symptoms. Thus, it appears that the rapid migration of PWNs induces a defence response throughout the seedling; however, this may not be effective in controlling these parasites, thereby ultimately leading to plant death..
||Kentaro Mishima, Tomonori Hirao, Miyoko Tsubomura, Miho Tamura, Manabu Kurita, Mine Nose, So Hanaoka, Makoto Takahashi, Atsushi Watanabe, Identification of novel putative causative genes and genetic marker for male sterility in Japanese cedar (Cryptomeria japonica D.Don), BMC Genomics, 10.1186/s12864-018-4581-5, 19, 1, 2018.04, Background: Japanese cedar (Cryptomeria japonica) is an important tree for Japanese forestry. Male-sterile marker development in Japanese cedar would facilitate selection of male-sterile plus trees, addressing the widespread social problem of pollinosis and facilitating the identification of heterozygotes, which are useful for breeding. Results: This study used next-generation sequencing for single-nucleotide polymorphism discovery in libraries constructed from several organs, including male-sterile and male-fertile strobili. The single-nucleotide polymorphisms obtained were used to construct a high-density linkage map, which enabled identification of a locus on linkage group 9 strongly correlated with male-sterile trait. Expressed sequence tags corresponding to 11 marker loci from 5 isotigs were associated with this locus within 33.4-34.5 cM. These marker loci explained 100% of the phenotypic variation. Several homologs of these sequences are associated with male sterility in rice or Arabidopsis, including a pre-mRNA splicing factor, a DEAD-box protein, a glycosyl hydrolase, and a galactosyltransferase. These proteins are thus candidates for the causal male-sterile gene at the ms-1 locus. After we used a SNaPshot assay to develop markers for marker-assisted selection (MAS), we tested F2 progeny between male-sterile and wild-type plus trees to validate the markers and extrapolated the testing to a larger plus-tree population. We found that two developed from one of the candidates for the causal gene were suitable for MAS. Conclusions: More than half of the ESTs and SNPs we collected were new, enlarging the genomic basis for genetic research on Japanese cedar. We developed two SNP markers aimed at MAS that distinguished individuals carrying the male-sterile trait with 100% accuracy, as well as individuals heterozygous at the male-sterile locus, even outside the mapping population. These markers should enable practical MAS for conifer breeding..
||Yuichiro Hiraoka, Ichiro Tamaki, Atsushi Watanabe, The origin of wild populations of Toxicodendron succedaneum on mainland Japan revealed by genetic variation in chloroplast and nuclear DNA, Journal of Plant Research, 10.1007/s10265-017-0992-7, 131, 2, 225-238, 2018.03, Toxicodendron succedaneum: (L.) Kuntze is a tree cultivated for the production of sumac wax, which is extracted from the mesocarp. There are several hypotheses regarding the origin of T. succedaneum on mainland Japan. In this study, the geographical distribution of genetic variation in 13 wild populations on Honshu, Shikoku, Kyushu, and Ryukyu Islands, Japan was investigated and compared with that of individuals from continental Asia. Seven chloroplast DNA haplotypes of T. succedaneum were observed in Japan and could be divided into three lineages based on relatedness between haplotypes. One of these lineages was also observed in continental Asia, and the others were genetically distant from the haplotypes that originated on the continent, with one considered to have originated on the Ryukyu Islands, and the other on mainland Japan. The genetic diversity of both chloroplast and nuclear DNA was lower in populations from Ryukyu Islands than in populations from mainland Japan. Bayesian clustering based on nuclear genotypes showed a clear difference between the groups from Ryukyu Islands and mainland Japan. Based on approximate Bayesian computation analysis of polymorphic data for both genomes, it was inferred that wild populations of T. succedaneum on mainland Japan consist of both lineages with natural distribution on mainland Japan and those introduced from Ryukyu Islands and continental Asia..
||Masakazu G. Iwaizumi, Shousuke Miyata, Tomonori Hirao, Miho Tamura, Atsushi Watanabe, Historical seed use and transfer affects geographic specificity in genetic diversity and structure of old planted Pinus thunbergii populations, Forest Ecology and Management, 10.1016/j.foreco.2017.10.026, 408, 211-219, 2018.01, Although most molecular ecology studies examining genetic variation have focused on natural forests, for some major tree species, natural forests are nearly extinct, and the remaining genetic resources are mainly planted forests. In order to manage the genetic variability and develop a conservation strategy for such species, it is important to examine genetic variation resulting from historical processes during repeated artificial population development through plantations. The geographic pattern of genetic diversity and structure of 49 old planted Pinus thunbergii populations (2755 trees) distributed across Japan was examined using seven nuclear microsatellite markers. We found that allelic diversity was generally lower in both northern and eastern populations; however, locally, some populations in other regions also exhibited low allelic diversity. The overall value of the standardized measure of population differentiation (G′ST = 0.206) was higher than that of both other widespread Japanese conifers and continental Pinus species. STRUCTURE software revealed a general gradual cline in genetic structure from southwestern to northeastern populations; however, some populations on the Japan Sea side showed quite a different local proportion of cluster memberships from nearby populations. These observations indicated that most of the preserved, planted populations of P. thunbergii possess regional genetic variation, but some populations were developed from seed pools derived from other regions, possibly through distribution by ship along the Japan Sea. Information on this specific genetic variation as a result of historical seed use and transfer should assist the design of several conservation units and breeding zones, while also taking care of a deep-seated need for conservation of pine forests by local people..
||Miyamoto, Naoko, Ono, Masako, 渡辺敦史, Construction of a core collection and evaluation of genetic resources for Cryptomeria japonica (Japanese cedar), JOURNAL OF FOREST RESEARCH, 10.1007/s10310-014-0460-3, 20, 1, 186-196, 2015.02.
||Nose Mine, 渡辺敦史, Clock genes and diurnal transcriptome dynamics in summer and winter in the gymnosperm Japanese cedar (Cryptomeria japonica (L.f.) D.Don), BMC PLANT BIOLOGY, 10.1186/s12870-014-0308-1, 14, 2014.11.
||K. Mishima, T. Fujiwara, T. Iki, K. Kuroda, K. Ymashita, M. Tamura, Y. Fujisawa, A. Watanabe, Transcriptome sequencing and profiling of expressed genes in cambial zone and differentiating xylem of Japanese cedar (Cryptomeria japonica) , BMC Genomics , 15, 219, 2014.03.
||Uchiyama, Kentaro, Iwata, Hiroyoshi, Moriguchi, Yoshinari, Ujino-Ihara, Tokuko, Ueno, Saneyoshi, Taguchi, Yuriko, Tsubomura, Miyoko, Mishima, Kentaro, Iki, Taiichi, 渡辺敦史, Futamura, Norihiro, Shinohara, Kenji, Tsumura, Yoshihiko, Demonstration of Genome-Wide Association Studies for Identifying Markers for Wood Property and Male Strobili Traits in Cryptomeria japonica, PLOS ONE, 10.1371/journal.pone.0079866, 8, 11, e79866, 2013.11.
||H. Ozawa, Watanabe Atsushi, Genetic diversity of Pinus densiflora pollen flowing over fragmented populations during a mating season, Journal of Forest Research, 17, 6, 488-498, 2012.12.