The Large-flowered Petunia (Petunia hybrida Vilm.) Genotype Promotes Expressions of Type-A Response Regulator and Cytokinin Receptor Genes like Cytokinin Response

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Expressions of the genes involved in the cytokinin (CK) phosphorelay signaling circuitry in petunia (Petunia hybrida Vilm.) were investigated with regard to the large-flowered trait induced by the semidominant Grandiflora (G) gene. We isolated three cDNAs encoding type-A response regulators (RRs, PhRR1-3) and one cDNA encoding CK receptor histidine protein kinase (PhHK). Expression levels of PhRR1-3 and PhHK in the developing corolla were markedly higher in large-flowered cultivars with the Gg genotype than in small- and medium-flowered cultivars with the gg genotype. Higher expression levels of PhRR1-3 and PhHK in the Gg than in the gg genotypes was also consistent in BC4 plants in which the genetic background except for G allele was mostly uniform. These results suggest that Gg genotype induces a high expression level of PhRR1-3 and PhHK. These changes in expression caused by the G allele were the same as those caused by the CK response. Since type-A RRs repress CK signaling, the G-allele-induced high expression levels of PhRR1-3 presumably have partial inhibitory effects on G-allele-induced corolla enlargement.
園芸学会の論文