Tissue culture-induced flower-color changes in Saintpaulia caused by excision of the transposon inserted in the flavonoid 3′, 5′ hydroxylase (F3′5′H) promoter

Abstract

The variegated Saintpaulia cultivar Thamires (Saintpaulia sp.), which has pink petals with blue splotches, is generally maintained by leaf cuttings. In contrast, tissue culture-derived progeny of the cultivar showed not only a high percentage of mutants with solid-blue petals but also other solid-color variants, which have not been observed from leaf cuttings. Solid-color phenotypes were inherited stably by their progeny from tissue culture. Petals from each solid-color variant were analyzed by high-performance liquid chromatography and shown to contain different proportions of three main anthocyanin derivatives: malvidin, peonidin, and pelargonidin. Analysis of flavonoid 3', 5'-hydroxylase (F3'5'H) sequences showed no differences in the coding region among the variants and variegated individuals. However, a transposon belonging to the hAT superfamily was found in the promoter region of variegated individuals, and the presence of transposon-related insertions or deletions correlated with the observed flower-color phenotypes. Solid-blue flower mutants contained 8-base pair (bp) insertions (transposon excision footprints), while solid-pink mutants had 58- to 70-bp insertions, and purple- and deep-purple mutants had 21- and 24-bp deletions, respectively. Real-time reverse transcription polymerase chain reaction (RT-PCR) analysis showed that F3'5'H expression levels correlated with insertions and deletions (indels) caused by hAT excision, resulting in flower-color differences. Our results showed that tissue culture of Saintpaulia 'Thamires' elicits transposon excision, which in turn alters F3'5'H expression levels and flower colors.

Acetylated Anthocyanidin 3-<i>O</i>-di-glycosides in Red-purple Flowers and Grayed-purple Leaves of <i>Saintpaulia</i> ‘Tomoko’

“…The distributions of 3-acetyl-rutinoside-5-glucosides of malvidin, pelargonidin, and peonidin have already been reported in the violet-blue, purple, and pink flowers of S. 'Thamires' as their main anthocyanins (Sato et al, 2011;Tatsuzawa et al, 2012). However, in this study, it was revealed that the red-purple flowers of S. 'Tomoko' contain peonidin 3-acetyl-rutinoside and cyanidin 3-acetyl-rutinoside as the main anthocyanins.…”

“…However, in this study, it was revealed that the red-purple flowers of S. 'Tomoko' contain peonidin 3-acetyl-rutinoside and cyanidin 3-acetyl-rutinoside as the main anthocyanins. Therefore, it is presumed that S. 'Tomoko' has two characteristic biosynthetic features different from S. 'Thamires' (Sato et al, 2011;Tatsuzawa et al, 2012) for producing the red-purple flowers as follows: (1) it is devoid of flavonoid 3',5'-hydroxylase activity and (2) 5-OH of anthocyanidin is free from glucosylation. On the other hand, anthocyanin in the grayed-purple colored leaves of S. 'Tomoko' contained cyanidin 3-acetylsambubioside as a main anthocyanin.…”

Plant biotechnology in support of the Millennium Goals II

“…An original research paper by Sato et al (2011) describes how somaclonal variation resulted in higher expression of a flavonoid due to transposon excision from a promoter region.…”

Cutting Leaves and Plant Growth Regulator Application Enhance Somaclonal Variation Induced by Transposition of VGs1 of Saintpaulia

“…is a suitable model plant to study somaclonal variation because adventitious shoots can easily regenerate from any organ and regeneration from leaves can occur independently of PGR addition. 'Thamires' has pink flowers caused by the pigment pelargonidin with blue splotches due to malvidin (Sato et al, 2011b). The purple variegations result from the deletion of a hAT superfamily TE, VGs1 (Variation Generator of Saintpaulia 1), inserted in the promoter region of flavonoid 3 ',5'-hydroxylase (F3'5'H), such that the transcription of F3'5'H is suppressed by the inactivation of a promoter by the inserted VGs1, belonging to the DNA-mediated TEs (called "class II"), such as Ac/Ds in Zea mays (Müller-Neumann et al, 1984) and Tam3 in Antirrhinum majus (Hehl et al, 1991), resulting in the suppression of malvidin synthesis (Sato et al, 2011b).…”

“…The purple variegations result from the deletion of a hAT superfamily TE, VGs1 (Variation Generator of Saintpaulia 1), inserted in the promoter region of flavonoid 3 ',5'-hydroxylase (F3'5'H), such that the transcription of F3'5'H is suppressed by the inactivation of a promoter by the inserted VGs1, belonging to the DNA-mediated TEs (called "class II"), such as Ac/Ds in Zea mays (Müller-Neumann et al, 1984) and Tam3 in Antirrhinum majus (Hehl et al, 1991), resulting in the suppression of malvidin synthesis (Sato et al, 2011b). In previous studies, we determined that the preexisting mutation percentage in the vegetative organ of this cultivar was < 3%, but that the percentages of somaclonal variations induced via adventitious shoots were much higher than 3% (Sato et al, 2011b). This finding indicates that the high levels of somaclonal variation did not occur in mutated but in wild-type cells, and VGs1 was activated in in vitro culture.…”