title: Evidence for maternal control of seed size in maize from phenotypic and transcriptional analysis.
abstract: Seed size is an important component of grain yield and a key determinant trait for crop domestication. The Krug Yellow Dent long-term selection experiment for large and small seed provides a valuable resource to dissect genetic and phenotypic changes affecting seed size within a common genetic background. In this study, inbred lines derived from Krug Large Seed (KLS) and Krug Small Seed (KSS) populations and reciprocal F1 crosses were used to investigate developmental and molecular mechanisms governing seed size. Seed morphological characteristics showed striking differences between KLS and KSS inbred lines, and the reciprocal cross experiment revealed a strong maternal influence on both seed weight and seed size. Quantification of endosperm area, starchy endosperm cell size, and kernel dry mass accumulation indicated a positive correlation between seed size, endosperm cell number, and grain filling rate, and patterns of grain filling in reciprocal crosses mirrored that of the maternal parent. Consistent with the maternal contribution to seed weight, transcriptome profiling of reciprocal F1 hybrids showed substantial similarities to the maternal parent. A set of differentially expressed genes between KLS and KSS inbreds were found, which fell into a broad number of functional categories including DNA methylation, nucleosome assembly, and heat stress response. In addition, gene co-expression network analysis of parental inbreds and reciprocal F1 hybrids identified co-expression modules enriched in ovule development and DNA methylation, implicating these two processes in seed size determination. These results expand our understanding of seed size regulation and help to uncover the developmental and molecular basis underlying maternal control of seed size in maize.
authors.affiliation: Department of Agronomy, University of Wisconsin-Madison, 1575 Linden Drive, Madison, WI 53706, USA.
authors.forename: Xia
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Department of Agronomy and Plant Genetics, University of Minnesota, St. Paul, MN 55108, USA.
authors.forename: Candice N
authors.initials: CN
authors.lastname: Hirsch
authors.affiliation: Department of Genetics and Biochemistry, Clemson University, Clemson, SC 29634, USA.
authors.forename: Rajandeep S
authors.initials: RS
authors.lastname: Sekhon
authors.affiliation: Department of Agronomy, University of Wisconsin-Madison, 1575 Linden Drive, Madison, WI 53706, USA DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, 1575 Linden Drive, Madison, WI 53706, USA.
authors.forename: Natalia
authors.initials: N
authors.lastname: de Leon
authors.affiliation: Department of Agronomy, University of Wisconsin-Madison, 1575 Linden Drive, Madison, WI 53706, USA DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, 1575 Linden Drive, Madison, WI 53706, USA smkaeppl@wisc.edu.
authors.forename: Shawn M
authors.initials: SM
authors.lastname: Kaeppler
mesh_terms: D003433:Crosses, Genetic; D056625:Endosperm / Q000235:genetics; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D053263:Gene Regulatory Networks; D017343:Genes, Plant; D006824:Hybridization, Genetic; D007178:Inbreeding; D009929:Organ Size / Q000235:genetics; D010641:Phenotype; D012639:Seeds / Q000033:anatomy & histology* / Q000235:genetics*; D014158:Transcription, Genetic; D003313:Zea mays / Q000033:anatomy & histology* / Q000235:genetics*
keywords: Endosperm; gene expression; maize; maternal effect; seed development; seed size.
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