Two distinct spontaneous mutations involved in white flower development in Lilium speciosum

Abstract

Lilium speciosum is one of the most important wild species used for breeding Oriental hybrid lily cultivars. Typical L. speciosum flowers possess red tepals and dark red anthers because of anthocyanin accumulation. However, white-flowered L. speciosum with two distinct phenotypes, one with white tepals and dark red anthers and the other with white tepals and yellow anthers, also exists. To elucidate the molecular mechanisms underlying white colouration, we isolated two regulatory genes and eight biosynthetic genes responsible for anthocyanin pigmentation in L. speciosum and compared these in red-and white-flowered lines. In the white tepal line with dark red anthers, we detected an amino acid substitution in the R2 repeat of LsMYB12, the R2R3-MYB that regulates tepal-specific anthocyanin biosynthesis, which led to reduced anthocyanin biosynthetic gene transcription and no tepal pigmentation. This LsMYB12 sequence was identical to that of an LhMYB12 in the white-flowered Oriental hybrid lily cultivar 'Rialto', indicating that this LsMYB12 sequence is present in lines that have been used for breeding. In addition, a nonsense mutation was detected in the dihydroflavonol 4-reductase (DFR) sequence of the white tepal line with yellow anthers, which resulted in a lack of anthocyanin accumulation in tepals and anthers. This mutated DFR has not been used for lily breeding because white tepal Oriental hybrid lily cultivars usually have dark red anthers. These results suggest that several mechanisms generate white flowers in lilies, and provide a substantial foundation for the production of Oriental hybrid lily cultivars with novel flower colour combinations.

<i>LhMYB12</i>, Regulating Tepal Anthocyanin Pigmentation in Asiatic Hybrid Lilies, is Derived from <i>Lilium dauricum</i> and <i>L. bulbiferum</i>

“…Therefore, to search for natural variations in the MYB12 genes of L. dauricum, L. bulbiferum, and L. cernuum will be crucial for producing novel color phenotypes in Asiatic hybrid lilies. In Oriental hybrid lilies, a spontaneous loss-of-function mutation in the MYB12 gene of L. speciosum has been used to breed white tepal cultivars (Suzuki et al, 2015).…”

Genome-wide association studies for inflorescence type and remontancy in Hydrangea macrophylla

“…Compared to traditional molecular markers, SNPs are abundant, stable, and easily detectable by sequencing technologies such as genotyping-bysequencing (GBS) even without a priori genome sequence information 13 . Thus, SNP markers have been widely used in genetic diversity assessments, molecular evolution studies, and genetic mapping for traits of interest in diverse horticultural crops such as carnation 14 , chrysanthemums 15 , roses 16 , lilies 17 , and tulips 18 .…”

Molecular determination and genetic modification of flower colour in Lilium spp

“…'Rialto' are thought to be white due to a single amino acid (W-to-L) mutation in the R2-repeat region of MYB12 transcription factor (Yamagishi, 2011;Yamagishi et al, 2012). A similar mutation has been found in MYB12 of L. speciosum having white tepals and red anthers (Suzuki et al, 2015).…”

“…Chalcone isomerase (CHI) subsequently catalyzes the isomerization of naringenin chalcone (tetrahydroxychalcone) to naringenin (Brugliera et al, 2013). Two CHI genes (CHIa and CHIb) are known to be involved in anthocyanin biosynthesis in the flowers of petunia (van Tunen et al 1988; and lily (Suzuki et al, 2015). Flavanone 3-hydroxylase (F3H) converts naringenin into dihydrokaempferol (Brugliera et al, 2013).…”

“…Over the years, many DFR genes from various plants have been characterized (Chu et al, 2014;Helariutta et al, 1993;Johnson et al, 1999). Lilium speciosum with mutated DFR display white flower colour (Suzuki et al, 2015). As the final step in the biosynthesis, anthocyanidin synthase (ANS) catalyzes the final oxidation of the colourless leucoanthocyanidins to coloured anthocyanidins -pelargonidin, cyanidin and delphinidin (Nakajima et al, 2001).…”