S-9 Genetic diversity and molecular mechanisms of reproductive systems in higher plants (S-9-1 - S-9-5)

2005 Genes & Genetic Systems  
Voltage-regulated phosphatase conserved among chordates A survey of the genome of the sea squirt Ciona intestinalis turned up an molecule with sequence similarity to both ion channels and phosphatase. This molecule, named as Ci-VSP, in fact functions as the voltage sensor just like voltage-gated ion channels and its enzymatic activity can be controlled by change across the cell membrane. Zebrafish homolog shows similar functional properties as Ci-VSP, although more depolarization is required
more » ... tion is required for tuning enzyme activity and movement of voltage sensor is slower. Widespread existence of homologous gene among chordates but not in non-chordates suggests that this signaling pathway is one of the innovations closely related to vertebrate-specific physiology and organs. S-8 -4 SUMIYAMA, Kenta 1 ( 1 Natl. Inst. Genet., Div. Popul. Genet.) Evolutionary multiple species comparison of genomic sequences: revealing remote cis-elements in clustered gene by transgenic mouse system. Recent expansion of genomic sequence data enables us to search for the functional elements that have not been identified by experiments yet. Here, cis-regulatory elements are focused on. Gene expression could be controlled by multiple factors, not simply by 5' upstream region (including promoter) but also by remote enhancers in either 5' upstream or 3' downstream region in vertebrate genomes. To reveal this sort of complex structure of gene regulatory system, comparisons of genome sequence from multiple species were conducted. Large scale comparison of genomic sequences among evolutionary closely related species can identify candidates of remote enhancers even if they are located far apart (like dozens of kilobases) from promoter. Together with transgenic animal system by using BAC/PAC transgene technique, candidates of enhancers can be functionally confirmed effectively. With enough number of species to be compared, individual transcription factor binding sites may be identified. Our research on the vertebrate Dlx gene system will be shown in this presentation as a successful example of an efficient combination of evolutionary genomics, bioinformatics and developmental biology. A gene network of floral transition in wheat The genetic control of floral transition or heading time in wheat is determined by three characters, vernalization requirement, photoperiodic sensitivity and narrow-sense earliness. Vernalization requirement refers to the sensitivity of the plant to cold treatment for accelerating spike primordium formation, and vernalization insensitivity is controlled mainly by three major genes, Vrn-A1, Vrn-B1 and Vrn-D1 located on chromosomes 5A, 5B and 5D, respectively. Wheat APETALA1 homolog WAP1 identified on the group 5 homoeologous chromosomes is identical with the Vrn genes. Photoperiodic (longday) response is controlled by three dominant Ppd genes, which have not been cloned. Narrow-sense earliness or earliness per se is the earliness of fully vernalized plants grown under long-day conditions, and involves polygenes with minor effects. Recent studies on the flowering-time genes in Arabidopsis revealed that SOC1/AGL20, FT and LFY are important regulators integrating multiple floral inductive signals. To clarify the molecular basis in flowering (heading) in wheat, we isolated and characterized the wheat homologs to SOC1/AGL20, FT and LFY genes, named WSOC1, WFT and WFL, respectively. Expression analyses indicate that WFT as well as WAP1 promote the floral transition by long-photoperiod and vernalization, whereas WSOC1 is associated with autonomous or/and gibberellin pathways. Ppd genes preventing the delay of heading under shortday condition is located on the different pathway from those required WAP1, WFT and WSOC1 genes. Based on the in situ hybridization experiment, we speculate that WFL may play a role in spikelet formation rather than floral meristem initiation in wheat. Adding our recent data about wheat orthologs of GIGANTIA and CONSTANS, we present a model of gene network for the floral transition in wheat. Grad.sch. Sci., Univ. Tokyo, 2 Natl. Inst. Basic Biol.) Genes controlling flower development and their evolution in rice To elucidate the function and evolution of genes that regulate flower development, we have been focusing on rice as a model plant for monocots. We report here the genetic mechanism of meristem size regulation and of floral organ specification in rice. The analysis of two FLORAL ORGAN NUMBER genes (FON1, FON2) revealed that CLAVATA (CLV) signaling system to regulate meristem maintenance was conserved in rice as in Arabidopsis. Molecular genetic studies on floral homeotic mutants showed that the YABBY gene DROOPING LEAF (DL) played a crucial function in carpel specification in rice. In Arabidopsis flower development, the AGAMOUS (AG) gene has multiple important functions such as stamen specification and floral meristem determinacy, in addition to carpel specification. We found that the functions controlled by AG in Arabidopsis were partially partitioned into two paralogous gene in rice, that is, stamen specification was mainly regulated by an AG-ortholog, OsMADS3, and floral meristem determinacy was primarily regulated by the other AG-ortholog, OsMADS58. These results suggest that C-class MADS box gene is subfunctionalized during evolution of rice. Genes Genet. Syst. (2005) 80 S-9 Genetic diversity and molecular mechanisms of reproductive systems in higher plants 436
doi:10.1266/ggs.80.436 fatcat:4p42wxyxqvbbffmbjglblk6r2i