The spatial expression and regulation of transcription factors IDEF1 and IDEF2.
OBJECTIVE
Under conditions of low iron availability, rice plants induce genes involved in iron uptake and utilization. The iron deficiency-responsive cis-acting element binding factors 1 and 2 (IDEF1 and IDEF2) regulate transcriptional response to iron deficiency in rice roots. Clarification of the functions of IDEF1 and IDEF2 could uncover the gene regulation mechanism.


METHODS
Spatial patterns of IDEF1 and IDEF2 expression were analysed by histochemical staining of IDEF1 and IDEF2 promoter-GUS transgenic rice lines. Expression patterns of the target genes of IDEF1 and IDEF2 were analysed using transformants with induced or repressed expression of IDEF1 or IDEF2 grown in iron-rich or in iron-deficient solutions for 1 d.


RESULTS
IDEF1 and IDEF2 were highly expressed in the basal parts of the lateral roots and vascular bundles. IDEF1 and IDEF2 expression was dominant in leaf mesophyll and vascular cells, respectively. These expression patterns were similar under both iron-deficient and iron-sufficient conditions. IDEF1 was strongly expressed in pollen, ovaries, the aleurone layer and embryo. IDEF2 was expressed in pollen, ovaries and the dorsal vascular region of the endosperm. During seed germination, IDEF1 and IDEF2 were expressed in the endosperm and embryo. Expression of IDEF1 target genes was regulated in iron-rich roots similar to early iron-deficiency stages. In addition, the expression patterns of IDEF2 target genes were similar between iron-rich conditions and early or subsequent iron deficiency.


CONCLUSIONS
IDEF1 and IDEF2 are constitutively expressed during both vegetative and reproductive stages. The spatial expression patterns of IDEF1 and IDEF2 overlap with their target genes in restricted cell types, but not in all cells. The spatial expression patterns and gene regulation of IDEF1 and IDEF2 in roots are generally conserved under conditions of iron sufficiency and deficiency, suggesting complicated interactions with unknown factors for sensing and transmitting iron-deficiency signals.
Kobayashi
Takanori
T
Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
Ogo
Yuko
Y
Aung
May Sann
MS
Nozoye
Tomoko
T
Itai
Reiko Nakanishi
RN
Nakanishi
Hiromi
H
Yamakawa
Takashi
T
Nishizawa
Naoko K
NK
D056625:Endosperm / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000235:genetics / Q000502:physiology; D012275:Oryza / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012639:Seeds / Q000235:genetics / Q000378:metabolism
D010940:Plant Proteins