Tsuyoshi Habu

De novo sequencing and comparative analysis of expressed sequence tags from gynodioecious fig (Ficus carica L.) fruits: caprifig and common fig

We conducted an exhaustive study of gene expression in fig fruits to identify the gene complexes responsible for fundamental fruit physiology and phenotypic differences between ecotypes. We performed high-throughput pyrosequencing on cDNA libraries constructed from caprifig and common fig fruits and compared their transcriptomes by analyzing the expressed sequence tags obtained. We collected a total of 290,594 expressed sequence tag reads from the two fruit types and assembled them into 71,455 unigenes (19,166 contigs and 52,289 singletons). We identified many metabolic genes, including those encoding proteins in the ethylene, glucose, and anthocyanin synthesis pathways that are involved in fruit maturation. This set also contained unigenes with unidentified functions. We observed no significant differences between the fruit types with respect to Gene Ontology term representation. By reverse transcription polymerase chain reaction, however, we detected several polymorphisms at the level of individual genes. Inter-type variations with respect to the expression level or transcription product size were observed in B- and C-class MADS-box gene homologs and chalcone synthase homologs, which are believed to be involved in sexuality and parthenocarpy, respectively. Expression polymorphisms were also observed for other genes, including a gibberellin-regulated protein gene. Our data and results contribute to genetic research on fig fruits and will aid in the understanding of fruit physiology and mechanisms of phenotypic differentiation.

Identification of RAN1 orthologue associated with sex determination through whole genome sequencing analysis in fig (Ficus carica L.)

With the aim of identifying sex determinants of fig, we generated the first draft genome sequence of fig and conducted the subsequent analyses. Linkage analysis with a high-density genetic map established by a restriction-site associated sequencing technique, and genome-wide association study followed by whole-genome resequencing analysis identified two missense mutations in RESPONSIVE-TO-ANTAGONIST1 (RAN1) orthologue encoding copper-transporting ATPase completely associated with sex phenotypes of investigated figs. This result suggests that RAN1 is a possible sex determinant candidate in the fig genome. The genomic resources and genetic findings obtained in this study can contribute to general understanding of Ficus species and provide an insight into figs and plants sex determination system.

The Prunus Self-Incompatibility Locus (S locus) Is Seldom Rearranged

Self-incompatibility enables flowering plants to discriminate between self- and non-selfpollen. In Prunus, the 2 genes determining specificity are the S-RNase (the female determinant that is a glycoprotein with ribonuclease activity) and the SFB (the male determinant, a protein with an F-box motif). In all Prunus S haplotypes characterized so far, with the exception of Prunus armeniaca S(2) haplotype, the 2 genes have opposite transcription orientations. Nevertheless, the relative transcription orientation observed in P. armeniaca S(2) haplotype has been postulated to be the one present in all S haplotypes from this species. We show that this is not the case by demonstrating that that the relative transcription orientation of the pollen and pistil genes of the P. armeniaca S(17) haplotype is that which is commonly found in Prunus. Using a phylogenetic approach, we show that the relative transcription orientation of the S-RNase and SFB genes is seldom changed (less than once every 380 million years). This contrasts with the Brassica sporophytic S locus where chromosomal rearrangements are often observed in the region between the pollen and pistil genes.