Dynamic expression of imprinted genes associates with maternally controlled nutrient allocation during maize endosperm development.
In angiosperms, the endosperm provides nutrients for embryogenesis and seed germination and is the primary tissue where gene imprinting occurs. To identify the imprintome of early developing maize (Zea mays) endosperm, we performed high-throughput transcriptome sequencing of whole kernels at 0, 3, and 5 d after pollination (DAP) and endosperms at 7, 10, and 15 DAP, using B73 by Mo17 reciprocal crosses. We observed gradually increased expression of paternal transcripts in 3- and 5-DAP kernels. In 7-DAP endosperm, the majority of the genes tested reached a 2:1 maternal versus paternal ratio, suggesting that paternal genes are nearly fully activated by 7 DAP. A total of 116, 234, and 63 genes exhibiting parent-specific expression were identified at 7, 10, and 15 DAP, respectively. The largest proportion of paternally expressed genes was at 7 DAP, mainly due to the significantly deviated parental allele expression ratio of these genes at this stage, while nearly 80% of the maternally expressed genes (MEGs) were specific to 10 DAP and were primarily attributed to sharply increased expression levels compared with the other stages. Gene ontology enrichment analysis of the imprinted genes suggested that 10-DAP endosperm-specific MEGs are involved in nutrient uptake and allocation and the auxin signaling pathway, coincident with the onset of starch and storage protein accumulation.
School of Plant Sciences, University of Arizona, Tucson, Arizona 85721-0036.
Mingming
M
Xin
Ruolin
R
Yang
Guosheng
G
Li
Hao
H
Chen
John
J
Laurie
Chuang
C
Ma
Dongfang
D
Wang
Yingyin
Y
Yao
Brian A
BA
Larkins
Qixin
Q
Sun
Ramin
R
Yadegari
Xiangfeng
X
Wang
Zhongfu
Z
Ni
D000483:Alleles; D001483:Base Sequence; D002454:Cell Differentiation; D019175:DNA Methylation; D056625:Endosperm / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000235:genetics*; D015723:Gene Library; D063990:Gene Ontology; D018745:Genome, Plant / Q000235:genetics*; D018392:Genomic Imprinting / Q000235:genetics*; D059014:High-Throughput Nucleotide Sequencing; D009928:Organ Specificity; D054817:Pollination; D020641:Polymorphism, Single Nucleotide; D018749:RNA, Plant / Q000737:chemistry / Q000235:genetics; D012639:Seeds / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D017423:Sequence Analysis, RNA; D013213:Starch / Q000378:metabolism; D059467:Transcriptome; D003313:Zea mays / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism
D018749:RNA, Plant; D013213:Starch