Transcriptions of MYB Gene and Anthocyanin Biosynthesis Genes In Oriental Hybrid Lily ‘Marrero' Are Suppressed by High Temperature

Anthocyanin is the major pigment in tepals of Oriental hybrid lily (Lilium spp.). We have identified the LhMYB12 gene, which encoded an AN2 type R2R3-MYB protein controlling anthocyanin biosynthesis in lily tepals. Here, we show that high temperature suppressed the transcriptions of LhMYB12 and anthocyanin biosynthesis genes resulting in poor coloration in flower tepals of Oriental hybrid lily ‘Marrero’. Potted ‘Marrero’ plants were grown in incubators at 20°C under a 16 h day-length. When the first flower was blooming, the plants were treated by high temperature at 35°C for two days while the control plants were kept at 20°C. In order to identify susceptible tepal stages to high temperature, the tepal development was divided into four stages according to the coloration. The tepals at stage 1 (St1) contained no anthocyanin. The tepals at stages 2 (St2), 3 (St3) and 4 (St4) contained anthocyanin pigments: pigmentation started at St2, pigmentation continued at St3, and the maximum pigmentation at St4. The buds for each stage were determined when the high temperature treatment started. After the treatment, all plants were continued to grow at 20°C, and flower tepals at full bloom were collected. Pigments and RNA were extracted from inner tepals. Anthocyanin contents were determined by absorbance at 515 nm. Transcriptions of LhMYB12, LhCHS, LhF3H and LhDFR were evaluated using quantitative RT-PCR. As a result, the most dramatic decrease in anthocyanin concentration was at St3. The anthocyanin concentration in the St3-tepals decreased by 80% at anthesis. However, the coloration of the St1 buds was not affected. This indicates that the susceptibility of lily buds to high temperature is dependent on their developmental stages. Transcriptions of LhMYB12, LhCHS, LhF3H and LhDFR were suppressed by the high temperature treatment. Because LhMYB12 regulates the transcription of anthocyanin biosynthesis genes, high temperature suppressed LhMYB12 transcription resulting in the decrease of biosynthesis gene expression and in poor accumulation of pigments.