title: Divergent functions of orthologous NAC transcription factors in wheat and rice.
abstract: The wheat GPC-B1 gene located on chromosome 6B is an early regulator of senescence and affects remobilization of protein and minerals to the grain. GPC-B1 is a NAC transcription factor and has a paralogous copy on chromosome 2B in wheat, GPC-B2. The closest rice homolog to both wheat GPC genes is Os07g37920 which is located on rice chromosome 7 and is colinear with GPC-B2. Since rice is a diploid species with a sequenced genome, we initiated the study of Os07g37920 to develop a simpler model to study senescence and mineral remobilization in cereals. We developed eleven independent RNA interference transgenic rice lines (Os07g37920-RNAi) and 10 over-expressing transgenic lines (Os07g37920-OE), but none of them showed differences in senescence. Transgenic Os07g37920-RNAi rice plants had reduced proportions of viable pollen grains and were male-sterile, but were able to produce seeds by cross pollination. Analysis of the flower morphology of the transgenic rice plants showed that anthers failed to dehisce. Transgenic Os07g37920-OE lines showed no sterility or anther dehiscence problems. Os07g37920 transcript levels were higher in stamens compared to leaves and significantly reduced in the transgenic Os07g37920-RNAi plants. Wheat GPC genes showed the opposite transcription profile (higher transcript levels in leaves than in flowers) and plants carrying knock-out mutations of all GPC-1 and GPC-2 genes exhibited delayed senescence but normal anther dehiscence and fertility. These results indicate a functional divergence of the homologous wheat and rice NAC genes and suggest the need for separate studies of the function and targets of these transcription factors in wheat and rice.
authors.affiliation: Department of Plant Sciences, University of California, Davis, CA 95616, USA.
authors.forename: Assaf
authors.initials: A
authors.lastname: Distelfeld
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Pearce
authors.forename: Raz
authors.initials: R
authors.lastname: Avni
authors.forename: Beatrice
authors.initials: B
authors.lastname: Scherer
authors.forename: Cristobal
authors.initials: C
authors.lastname: Uauy
authors.forename: Fernando
authors.initials: F
authors.lastname: Piston
authors.forename: Ann
authors.initials: A
authors.lastname: Slade
authors.forename: Rongrong
authors.initials: R
authors.lastname: Zhao
authors.forename: Jorge
authors.initials: J
authors.lastname: Dubcovsky
mesh_terms: D000375:Aging; D032461:Chromosomes, Plant; D019143:Evolution, Molecular; D035264:Flowers / Q000235:genetics / Q000378:metabolism; D055786:Gene Knockout Techniques; D008957:Models, Genetic; D012275:Oryza / Q000235:genetics*; D010802:Phylogeny; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D054817:Pollination; D034622:RNA Interference; D012639:Seeds / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism*; D014908:Triticum / Q000235:genetics*
chemical_list: D010940:Plant Proteins; D014157:Transcription Factors