title: Unique morphological changes in plant pathogenic phytoplasma-infected petunia flowers are related to transcriptional regulation of floral homeotic genes in an organ-specific manner.
abstract: Abnormal flowers are often induced by infection of certain plant pathogens, e.g. phytoplasma, but the molecular mechanisms underlying these malformations have remained poorly understood. Here, we show that infection with OY-W phytoplasma (Candidatus Phytoplasma asteris, onion yellows phytoplasma strain, line OY-W) affects the expression of the floral homeotic genes of petunia plants in an organ-specific manner. Upon infection with OY-W phytoplasma, floral morphological changes, including conversion to leaf-like structures, were observed in sepals, petals and pistils, but not in stamens. As the expression levels of homeotic genes differ greatly between floral organs, we examined the expression levels of homeotic genes in each floral organ infected by OY-W phytoplasma, compared with healthy plants. The expression levels of several homeotic genes required for organ development, such as PFG, PhGLO1 and FBP7, were significantly downregulated by the phytoplasma infection in floral organs, except the stamens, suggesting that the unique morphological changes caused by the phytoplasma infection might result from the significant decrease in expression of some crucial homeotic genes. Moreover, the expression levels of TER, ALF and DOT genes, which are known to participate in floral meristem identity, were significantly downregulated in the phytoplasma-infected petunia meristems, implying that phytoplasma would affect an upstream signaling pathway of floral meristem identity. Our results suggest that phytoplasma infection may have complex effects on floral development, resulting in the unique phenotypes that were clearly distinct from the mutant flower phenotypes produced by the knock-out or the overexpression of certain homeotic genes.
authors: Department of Agricultural and Environmental Biology, Laboratory of Plant Pathology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan.
authors: Misako
authors: M
authors: Himeno
authors: Yutaro
authors: Y
authors: Neriya
authors: Nami
authors: N
authors: Minato
authors: Chihiro
authors: C
authors: Miura
authors: Kyoko
authors: K
authors: Sugawara
authors: Yoshiko
authors: Y
authors: Ishii
authors: Yasuyuki
authors: Y
authors: Yamaji
authors: Shigeyuki
authors: S
authors: Kakizawa
authors: Kenro
authors: K
authors: Oshima
authors: Shigetou
authors: S
authors: Namba