title: Anatomical and transcriptional dynamics of maize embryonic leaves during seed germination.
abstract: Our anatomical analysis revealed that a dry maize seed contains four to five embryonic leaves at different developmental stages. Rudimentary kranz structure (KS) is apparent in the first leaf with a substantial density, but its density decreases toward younger leaves. Upon imbibition, leaf expansion occurs rapidly with new KSs initiated from the palisade-like ground meristem cells in the middle of the leaf. In parallel to the anatomical analysis, we obtained the time course transcriptomes for the embryonic leaves in dry and imbibed seeds every 6 h up to hour 72. Over this time course, the embryonic leaves exhibit transcripts of 30,255 genes at a level that can be regarded as "expressed." In dry seeds, ∼25,500 genes are expressed, showing functional enrichment in transcription, RNA processing, protein synthesis, primary metabolic pathways, and calcium transport. During the 72-h time course, ∼13,900 genes, including 590 transcription factor genes, are differentially expressed. Indeed, by 30 h postimbibition, ∼2,200 genes expressed in dry seeds are already down-regulated, and ∼2,000 are up-regulated. Moreover, the top 1% expressed genes at 54 h or later are very different from those before 30 h, reflecting important developmental and physiological transitions. Interestingly, clusters of genes involved in hormone metabolism, signaling, and responses are differentially expressed at various time points and TF gene expression is also modular and stage specific. Our dataset provides an opportunity for hypothesizing the timing of regulatory actions, particularly in the context of KS development.
authors: Biodiversity Research Center, Academia Sinica, Taipei 115, Taiwan.
authors: Wen-Yu
authors: WY
authors: Liu
authors: Yao-Ming
authors: YM
authors: Chang
authors: Sean Chun-Chang
authors: SC
authors: Chen
authors: Chen-Hua
authors: CH
authors: Lu
authors: Yeh-Hwa
authors: YH
authors: Wu
authors: Mei-Yeh Jade
authors: MY
authors: Lu
authors: Di-Rong
authors: DR
authors: Chen
authors: Arthur Chun-Chieh
authors: AC
authors: Shih
authors: Chiou-Rong
authors: CR
authors: Sheue
authors: Hsuan-Cheng
authors: HC
authors: Huang
authors: Chun-Ping
authors: CP
authors: Yu
authors: Hsin-Hung
authors: HH
authors: Lin
authors: Shin-Han
authors: SH
authors: Shiu
authors: Maurice Sun-Ben
authors: MS
authors: Ku
authors: Wen-Hsiung
authors: WH
authors: Li
mesh_terms: D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D018525:Germination / Q000235:genetics; D010937:Plant Growth Regulators / Q000235:genetics; D018515:Plant Leaves / Q000196:embryology / Q000235:genetics; D010940:Plant Proteins / Q000235:genetics; D018749:RNA, Plant / Q000235:genetics; D012639:Seeds / Q000196:embryology / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics; D003313:Zea mays / Q000196:embryology* / Q000235:genetics* / Q000502:physiology
chemical_list: D010937:Plant Growth Regulators; D010940:Plant Proteins; D018749:RNA, Plant; D014157:Transcription Factors