Mutant <i>PI/GLO</i> Homolog Confers the Hose-in-hose Flower Phenotype in Kurume Azaleas

Abstract

To analyze hose-in-hose flowers of Kurume azaleas, floral morphologies and homeotic MADS genes were investigated in single and hose-in-hose cultivars. In floral morphological analysis, single flowers are comprised of four whorls of floral organs: sepals, petals, stamens, and carpels. Hose-in-hose flowers, in contrast, produced petaloid sepals instead of sepals in the first whorl. Based on molecular analysis, we isolated PISTILLATA (PI)/GLOBOSA (GLO) homologs in the hose-in-hose flower cultivar 'Kirin' and analyzed their expression in single flower and hose-in-hose flower cultivars. The mRNA sequences of two RoPI genes, RoPI-1 and RoPI-2, differed in terms of a 6 bp deletion. Based on genomic analysis, an insertion sequence was found in the second intron of RoPI-1 in hose-in-hose flowers. These RoPI genes were mainly expressed in the second and third whorls of single flowers, whereas these genes were expressed in all whorls of hose-in-hose flowers. These results suggest that the up-regulation of RoPI-1 expression contributed to the petaloid sepal formation of hosein-hose flowers of Kurume azaleas.

Long-lasting Corolla Cultivars in Japanese Azaleas: A Mutant AP3/DEF Homolog Identified in Traditional Azalea Cultivars from More Than 300 Years Ago

“…The length of the corolla and the width of the corolla lobe were measured in 3–10 fully expanded flowers per individual plant ( Hang et al, 2010 ; Gobara et al, 2017 ). The observation of abaxial epidermal cells was performed using a Scanning Electron Microscope ( HITACHI TM3000 ) ( Cheon et al, 2016 ). The stomatal density of abaxial surface in the corolla was determined using Suzuki’s Universal Microprinting Method ( SUMP; SUMP Laboratory ) and a light microscope ( Nikon ) ( Tasaki et al, 2012b ).…”

“…In a previous study, we isolated two full-length sequences of PI/GLO from R. obtusum ( Cheon et al, 2016 ) and a partial length of the AP3/DEF homolog from R. pulchrum ( Cheon et al, 2011 ) and reported that PI/GLO and AP3/DEF homologs participated in corolla development in the evergreen azaleas ( Tasaki et al, 2012a ; Cheon et al, 2016 ). In this study, to further characterize long-lasting flowers in evergreen azaleas, including R. kaempferi ‘Nikkō-misome,’ R. macrosepalum ‘Kochō-zoroi,’ R. indicum ‘Chōjyu-hō,’ and R. × hannoense ‘Amagi-beni-chōjyu,’ and to understand how mutant genes result in long-lasting flowers, we investigated the floral morphologies and B-class genes using the cultivars and progenies from a cross between normal and long-lasting flowers.…”