Toshinori Ochiai

Characterization of TrcMADS1 gene of Trillium camtschatcense (Trilliaceae) reveals functional evolution of the SOC1/TM3-like gene family

Plant MADS-box genes encode transcriptional regulators that are critical for a number of developmental processes, such as the establishment of floral organ identity, flowering time, and fruit development. It appears that the MADS-box gene family has undergone considerable gene duplication and divergence within various angiosperm lineages. SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1)/Tomato MADS-box gene 3 (TM3)-like genes are members of the MADS-box gene family and have undergone repeated duplication events. Here, we isolated and characterized the SOC1/TM3-like gene TrcMADS1 from Trillium camtschatcense (Trilliaceae) to infer the ancestral function of SOC1/TM3-like genes. The alignment of SOC1/TM3-like genes revealed the presence of a highly conserved region in the C-terminal of predicted protein sequences, designated the SOC1 motif. Phylogenetic analysis indicated that TrcMADS1 is at the basal position of the SOC1/TM3-like gene family. The TrcMADS1 mRNA was detected in both vegetative and reproductive organs by RT-PCR. Our results suggest that duplicated copies of SOC1/TM3-like gene evolved to become variously functionally specialized.

Molecular phylogeny and evolution of alcohol dehydrogenase (Adh) genes in legumes

BackgroundNuclear genes determine the vast range of phenotypes that are responsible for the adaptive abilities of organisms in nature. Nevertheless, the evolutionary processes that generate the structures and functions of nuclear genes are only now be coming understood. The aim of our study is to isolate the alcohol dehydrogenase (Adh) genes in two distantly related legumes, and use these sequences to examine the molecular evolutionary history of this nuclear gene.ResultsWe isolated the expressed Adh genes from two species of legumes, Sophora flavescens Ait. and Wisteria floribunda DC., by a RT-PCR based approach and found a new Adh locus in addition to homologues of the Adh genes found previously in legumes. To examine the evolution of these genes, we compared the species and gene trees and found gene duplication of the Adh loci in the legumes occurred as an ancient event.ConclusionThis is the first report revealing that some legume species have at least two Adh gene loci belonging to separate clades. Phylogenetic analyses suggest that these genes resulted from relatively ancient duplication events.

AVAG2 is a putative D-class gene from an ornamental asparagus

Members of the AGAMOUS (AG) family of MADS-box genes play important roles in regulating the development of reproductive organs in flowering plants. To elucidate the molecular mechanisms of floral development in Asparagus virgatus, we isolated and characterized an Asparagus AG-homologue, AVAG2. AVAG2 contains an open reading frame that encodes a deduced protein with 234 amino acid residues. Phylogenetic analysis indicated that AVAG2 belongs to the D-lineage of the AG gene family. AVAG2 mRNA was detected in the flower, but not in vegetative organs. Moreover, in in situ hybridization experiments, AVAG2 signals were observed in the stamens and carpels during early flower development, and appeared in the ovule only at later developmental stages. This suggests that the AVAG2 gene is involved in ovule formation. Thus, our expression data support the phylogenetic analysis indicating that AVAG2 belongs to the D-class gene family.

The structure and expression of SEPALLATA-like genes in Asparagus species (Asparagaceae)

MADS-box genes encode transcriptional regulators that are critical for a number of developmental processes. In the MADS-box gene family, the SEPALLATA (SEP) gene subfamily plays an important role in controlling the development of floral organs in flowering plants. To understand the molecular mechanisms of floral development in Asparagus, we isolated and characterized several SEP-like genes from dioecious Asparagus officinalis and hermaphrodite A. virgatus: AOMADS1, AOMADS2, AOMADS3, and AVMADS1, AVMADS2, AVMADS3, respectively. Through alignment of the predicted amino acid sequences of various SEP-like genes, we defined three characteristic motifs in the C-terminal region of the genes: SEP motif I, SEP/AGL6 motif, and SEP motif II. Of the genes we isolated, AOMADS3 and AVMADS3 had lost the SEP motif II. Phylogenetic analysis revealed that AOMADS1, AOMADS2, AVMADS1, and AVMADS2 were closely related to SEP3 from Arabidopsis, whereas AOMADS3 and AVMADS3 were classified in different clade which is far related to SEP3 gene. Northern hybridization and RT-PCR showed that three SEP-like genes in A. officinalis were specifically expressed in the flower buds. In addition, PCR RFLP showed that there was no significant difference in the amount of transcripts of AOMADS1 and AOMADS2. These results suggest that AOMADS1 and AOMADS2 may be redundant genes. In contrast, the expression of AOMADS3 was weaker than that of AOMADS1 or AOMADS2, suggesting that the function of AOMADS3 may be different than that of AOMADS1 or AOMADS2.