Genetic demonstration of the involvement of WUSCHEL-related homeobox (WOX) genes in narrow-petal and narrow-leaf mutations in traditional Japanese azalea cultivars
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The spider-type azalea cultivars, Rhododendron kaempferi ‘Kin-kujyaku’ and Rhododendron macrosepalum ‘Seigaiha’, are characterized by extremely narrow leaves and choripetalous flowers with narrow petals. Previous morphological analysis of these cultivars revealed that narrowed organs would be a common mutation in the growth of lateral organs in the transverse plane. In the present study, we focused on the analysis of WUSCHEL-related homeobox (WOX) genes, WOX1 and WOX3, which regulate the laminar width and development of lateral organs. Sequence analysis of the two genes confirmed a fatal mutation in Rk/RmWOX3/SPIDER of ‘Kin-kujyaku’ and ‘Seigaiha’. To demonstrate the role of SPIDER in the spider-type phenotype in azalea, we performed genotyping using DNA markers developed for multiplex PCR that can distinguish between the wild-type and the spider-type allele based on the partial mutated region of RkWOX3/SPIDER in ‘Kin-kujyaku’. The investigation of BC1 population derived from ‘Kin-kujyaku’ confirmed complete co-segregation between spider-type mutation and Rkwox3/spider band pattern of DNA markers. Therefore, we concluded that SPIDER is responsible for the spider-type mutation in azalea.
KeywordsChoripetalous flower Molecular marker Narrow mutation WOX3 WUSCHEL-related homeobox gene
This study was supported by Grant-in-Aid for Scientific Research (KAKENHI Nos. 26292017, 18K05617) from Japan Society for the Promotion of Science (JSPS). The authors thank the faculty of Life and Environmental Science at Shimane University for their help and financial support of this study.
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