Ideal Plant Architecture 1 (IPA1) encodes SQUAMOSA PROMOTER BINDING PROTEIN-LIKE 14 (SPL14) with a pleiotropic effect on regulating rice development and biotic stress responses. To investigate the role of
IPA1 in early seedling development, we developed a pair of
IPA1/
ipal-NILs
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Ideal Plant Architecture 1 (IPA1) encodes SQUAMOSA PROMOTER BINDING PROTEIN-LIKE 14 (SPL14) with a pleiotropic effect on regulating rice development and biotic stress responses. To investigate the role of
IPA1 in early seedling development, we developed a pair of
IPA1/
ipal-NILs and found that seed germination and early seedling growth were retarded in the
ipa1-NIL. Analysis of the soluble sugar content, activity of amylase, and expression of the
α-amylase genes revealed that the starch metabolism was weakened in the
ipa1-NIL germinating seeds. Additionally, the content of bioactive gibberellin (GA) was significantly lower than that in the
IPA1-NIL seeds at 48 h of imbibition. Meanwhile, the expression of GA synthesis-related gene
OsGA20ox1 was downregulated, whereas the expression of GA inactivation-related genes was upregulated in
ipa1-NIL seeds. In addition, the expression of
OsWRKY51 and
OsWRKY71 was significantly upregulated in
ipa1-NIL seeds. Using transient dual-luciferase and yeast one-hybrid assays, IPA1 was found to directly activate the expression of
OsWRKY51 and
OsWRKY71, which would interfere with the binding affinity of GA-induced transcription factor OsGAMYB to inhibit the expression of
α-amylase genes. In summary, our results suggest that
IPA1 negatively regulates seed germination and early seedling growth by interfering with starch metabolism via the GA and
WRKY pathways.
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