RETARDED GROWTH OF EMBRYO1, a new basic helix-loop-helix protein, expresses in endosperm to control embryo growth.
We have isolated two dominant mutants from screening approximately 50,000 RIKEN activation-tagging lines that have short inflorescence internodes. The activation T-DNAs were inserted near a putative basic helix-loop-helix (bHLH) gene and expression of this gene was increased in the mutant lines. Overexpression of this bHLH gene produced the original mutant phenotype, indicating it was responsible for the mutants. Specific expression was observed during seed development. The loss-of-function mutation of the RETARDED GROWTH OF EMBRYO1 (RGE1) gene caused small and shriveled seeds. The embryo of the loss-of-function mutant showed retarded growth after the heart stage although abnormal morphogenesis and pattern formation of the embryo and endosperm was not observed. We named this bHLH gene RGE1. RGE1 expression was determined in endosperm cells using the beta-glucuronidase reporter gene and reverse transcription-polymerase chain reaction. Microarray and real-time reverse transcription-polymerase chain reaction analysis showed specific down-regulation of putative GDSL motif lipase genes in the rge1-1 mutant, indicating possible involvement of these genes in seed morphology. These data suggest that RGE1 expression in the endosperm at the heart stage of embryo development plays an important role in controlling embryo growth.
Plant Functional Genomics Research Group, RIKEN Plant Science Center, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan.
Youichi
Y
Kondou
Miki
M
Nakazawa
Mika
M
Kawashima
Takanari
T
Ichikawa
Takeshi
T
Yoshizumi
Kumiko
K
Suzuki
Akie
A
Ishikawa
Tomoko
T
Koshi
Ryo
R
Matsui
Shu
S
Muto
Minami
M
Matsui
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000196:embryology* / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D051792:Basic Helix-Loop-Helix Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D020869:Gene Expression Profiling; D018257:Helix-Loop-Helix Motifs; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D020411:Oligonucleotide Array Sequence Analysis; D010641:Phenotype; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012639:Seeds / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D016415:Sequence Alignment
D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D012333:RNA, Messenger; C532182:RETARDED GROWTH OF EMBRYO1 protein, Arabidopsis