title: Cell Number Regulator1 affects plant and organ size in maize: implications for crop yield enhancement and heterosis.
abstract: Genes involved in cell number regulation may affect plant growth and organ size and, ultimately, crop yield. The tomato (genus Solanum) fruit weight gene fw2.2, for instance, governs a quantitative trait locus that accounts for 30% of fruit size variation, with increased fruit size chiefly due to increased carpel ovary cell number. To expand investigation of how related genes may impact other crop plant or organ sizes, we identified the maize (Zea mays) gene family of putative fw2.2 orthologs, naming them Cell Number Regulator (CNR) genes. This family represents an ancient eukaryotic family of Cys-rich proteins containing the PLAC8 or DUF614 conserved motif. We focused on native expression and transgene analysis of the two maize members closest to Le-fw2.2, namely, CNR1 and CNR2. We show that CNR1 reduced overall plant size when ectopically overexpressed and that plant and organ size increased when its expression was cosuppressed or silenced. Leaf epidermal cell counts showed that the increased or decreased transgenic plant and organ size was due to changes in cell number, not cell size. CNR2 expression was found to be negatively correlated with tissue growth activity and hybrid seedling vigor. The effects of CNR1 on plant size and cell number are reminiscent of heterosis, which also increases plant size primarily through increased cell number. Regardless of whether CNRs and other cell number-influencing genes directly contribute to, or merely mimic, heterosis, they may aid generation of more vigorous and productive crop plants.
authors.affiliation: Pioneer Hi-Bred, a DuPont Business, Johnston, IA 50131, USA. mei.guo@pioneer.com
authors.forename: Mei
authors.initials: M
authors.lastname: Guo
authors.forename: Mary A
authors.initials: MA
authors.lastname: Rupe
authors.forename: Jo Ann
authors.initials: JA
authors.lastname: Dieter
authors.forename: Jijun
authors.initials: J
authors.lastname: Zou
authors.forename: Daniel
authors.initials: D
authors.lastname: Spielbauer
authors.forename: Keith E
authors.initials: KE
authors.lastname: Duncan
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Howard
authors.forename: Zhenglin
authors.initials: Z
authors.lastname: Hou
authors.forename: Carl R
authors.initials: CR
authors.lastname: Simmons
mesh_terms: D018533:Biomass; D018556:Crops, Agricultural / Q000235:genetics / Q000254:growth & development; D004269:DNA, Bacterial / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D006823:Hybrid Vigor; D008958:Models, Molecular; D005810:Multigene Family; D010641:Phenotype; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000254:growth & development; D018749:RNA, Plant / Q000235:genetics; D016415:Sequence Alignment; D003313:Zea mays / Q000235:genetics* / Q000254:growth & development*
chemical_list: D004269:DNA, Bacterial; D010940:Plant Proteins; D018749:RNA, Plant; C036483:T-DNA
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