Article

Indirect ABA-dependent regulation of seed storage protein genes by FUSCA3 transcription factor in Arabidopsis.

Life Science Research Center, Mie University, Tsu, 514-8507 Japan.
Plant and Cell Physiology (impact factor: 4.7). 03/2005; 46(2):300-11. DOI:10.1093/pcp/pci031 pp.300-11
Source: PubMed

ABSTRACT The key transcription factors that control seed maturation, ABSCISIC ACID INSENSITIVE3 (ABI3) and FUSCA3 (FUS3), share homologous DNA-binding domains. Regulation of seed storage protein genes At2S3 and CRC by ABI3 and FUS3 was investigated using transgenic plants in which ABI3 and FUS3 could be ectopically induced by steroid hormones. Like ABI3, the presence of FUS3 led to expression of At2S3 and CRC in vegetative tissues. FUS3-mediated induction of CRC was completely dependent on exogenous abscisic acid (ABA), while At2S3 was weakly induced without ABA but strongly enhanced with ABA. This ABA dependency of FUS3-induced CRC and At2S3 expression was similar to that observed for ABI3. However, kinetic analysis revealed distinctions between the mechanisms of ABA-dependent CRC regulation by FUS3 or ABI3, and between target genes. While At2S3 activation by FUS3 was rapid, CRC induction by FUS3 in the presence of ABA, and by ABA followed by the presence of FUS3, took a significantly longer time (24-36 h). This suggested the involvement of an indirect mechanism requiring the ABA- and FUS3-dependent synthesis of intermediate regulatory factor(s). A chimeric protein composed of the FUS3 B3 domain, and a heterologous activation domain and nuclear localization signal exhibited a tight coupling with ABA regulation as observed for wild-type FUS3. Simultaneous induction of FUS3 and ABI3 did not result in the synergistic activation of CRC and At2S3. Based on these results, similarities and differences in the mechanisms of seed storage protein gene regulation by FUS3 and ABI3 are discussed.

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Keywords

ABA dependency
 
ABA regulation
 
ABA-dependent CRC regulation
 
ABSCISIC ACID INSENSITIVE3
 
At2S3 activation
 
control seed maturation
 
exogenous abscisic acid
 
FUS3 B3 domain
 
heterologous activation domain
 
intermediate regulatory factor(s)
 
key transcription factors
 
kinetic analysis
 
nuclear localization signal exhibited
 
seed storage protein gene regulation
 
seed storage protein genes At2S3
 
share homologous DNA-binding domains
 
steroid hormones
 
synergistic activation
 
target genes
 
wild-type FUS3
 

Yasuaki Kagaya