Project description:Symplocarpus renifolius is a member of Araceae family that is extraordinarily diverse in appearance. Previous studies on chloroplast genomes in Araceae were focused on duckweeds (Lemnoideae) and root crops (Colocasia, commonly known as taro). Here, we determined the chloroplast genome of Symplocarpus renifolius and compared the factors, such as genes and inverted repeat (IR) junctions and performed phylogenetic analysis using other Araceae species. The chloroplast genome of S. renifolius is 158,521 bp and includes 113 genes. A comparison among the Araceae chloroplast genomes showed that infA in Lemna, Spirodela, Wolffiella, Wolffia, Dieffenbachia and Colocasia has been lost or has become a pseudogene and has only been retained in Symplocarpus. In the Araceae chloroplast DNA (cpDNA), psbZ is retained. However, psbZ duplication occurred in Wolffia species and tandem repeats were noted around the duplication regions. A comparison of the IR junction in Araceae species revealed the presence of ycf1 and rps15 in the small single copy region, whereas duckweed species contained ycf1 and rps15 in the IR region. The phylogenetic analyses of the chloroplast genomes revealed that Symplocarpus are a basal group and are sister to the other Araceae species. Consequently, infA deletion or pseudogene events in Araceae occurred after the divergence of Symplocarpus and aquatic plants (duckweeds) in Araceae and duplication events of rps15 and ycf1 occurred in the IR region.
Project description:Symplocarpus nipponicus, a member of the Araceae family, is an endangered plant in several prefectures in Japan. For the conservation of this wild species, we investigated the morphology, life cycle, and genetic diversity of three wild populations. By fixed-point observation over several years, we found that it takes at least four years for the plant to set the inflorescences consisting of spadices and spathes, and another two years for it to set mature seeds. To examine the genetic diversity in the wild population, we developed 11 novel microsatellite markers and investigated the genetic variation in three populations in Kyoto Prefecture: Ayabe, Hanase, and Momoi. The Ayabe population carried less genetic variation than the other two areas, suggesting the isolation of the habitat and thus a higher risk of extinction. Our results provide basic knowledge of the ecological aspects of S. nipponicus, as well as molecular techniques for the assessment of its genetic diversity, and thus are useful for the conservation of this endangered species.
Project description:Floral thermogenesis has been found in dozens of primitive seed plants and the reproductive organs in these plants produce heat during anthesis. Thus, characterization of the molecular mechanisms underlying flowering is required to fully understand the role of thermogenesis, but this aspect of thermogenic plant development is largely unknown. In this study, extensive database searches and cloning experiments suggest that thermogenic skunk cabbage (Symplocarpus renifolius), which is a member of the family Araceae, possesses two genes encoding phosphatidyl ethanolamine-binding proteins (PEBP), FLOWERING LOCUS T (SrFT) and MOTHER OF FT AND TFL1 (SrMFT). Functional analyses of SrFT and SrMFT in Arabidopsis indicate that SrFT promotes flowering, whereas SrMFT does not. In S. renifolius, the stage- and tissue-specific expression of SrFT was more evident than that of SrMFT. SrFT was highly expressed in flowers and leaves and was mainly localized in fibrovascular tissues. In addition, microarray analysis revealed that, within floral tissues, SrFT was co-regulated with the genes associated with cellular respiration and mitochondrial function, including ALTERNATIVE OXIDASE gene proposed to play a major role in floral thermogenesis. Taken together, these data suggest that, among the PEBP genes, SrFT plays a role in flowering and floral development in the thermogenic skunk cabbage.
Project description:Thermogenesis in plants involves significant increases in their cyanide-resistant mitochondrial alternative oxidase (AOX) capacity. Because AOX is a non-proton-motive ubiquinol oxidase, the dramatic drop in free energy between ubiquinol and oxygen is dissipated as heat. In the thermogenic skunk cabbage (Symplocarpus renifolius), SrAOX is specifically expressed in the florets. Although SrAOX harbours conserved cysteine residues, the details of the mechanisms underlying its redox regulation are poorly understood. In our present study, the two mitochondrial thioredoxin o cDNAs SrTrxo1 and SrTrxo2, were isolated from the thermogenic florets of S. renifolius. The deduced amino acid sequences of the protein products revealed that SrTrxo2 specifically lacks the region corresponding to the α3-helix in SrTrxo1. Expression analysis of thermogenic and non-thermogenic S. renifolius tissues indicated that the SrTrxo1 and SrAOX transcripts are predominantly expressed together in thermogenic florets, whereas SrTrxo2 transcripts are almost undetectable in any tissue. Finally, functional in vitro analysis of recombinant SrTrxo1 and mitochondrial membrane fractions of thermogenic florets indicated its reducing activity on SrAOX proteins. Taken together, these results indicate that SrTrxo1 is likely to play a role in the redox regulation of SrAOX in S. renifolius thermogenic florets.