Sugar signalling mediates cluster root formation and phosphorus starvation-induced gene expression in white lupin

Cluster root (CR) formation contributes much to the adaptation to phosphorus (P) deficiency. CR formation by white lupin (Lupinus albus L.) is affected by the P-limiting level in shoots, but not in roots. Thus, shoot-derived signals have been expected to transmit the message of P-deficiency to stimulate CR formation. In this study, it is shown that sugars are required for a response to P starvation including CR formation and the expression of P starvation-induced genes. White lupin plants were grown in vitro on P-sufficient or P-deficient media supplemented with sucrose for 4 weeks. Sucrose supply stimulated CR formation in plants on both P-sufficient and P-deficient media, but no CR appeared on the P-sufficient medium without sucrose. Glucose and fructose also stimulated CR formation on the P-sufficient medium. On the medium with sucrose, a high concentration of inorganic phosphate in leaves did not suppress CR formation. Because sorbitol or organic acid in the media did not stimulate CR formation, the sucrose effect was not due to increased osmotic pressure or enriched energy source, that is, sucrose acted as a signal. Gene transcription induced by P starvation, LaPT1 and LaPEPC3, was magnified by the combination of P limitation and sucrose feeding, and that of LaSAP was stimulated by sucrose supply independently of P supply. These results suggest that at least two sugar-signalling mediating systems control P starvation responses in white lupin roots. One system regulates CR formation and LaSAP expression, which acts even when P is sufficient if roots receive sugar as a signal. The other system controls LaPT1 and LaPEPC3 expression, which acts when P is insufficient

RNA-seq-based evaluation of bicolor tepal pigmentation in Asiatic hybrid lilies (Lilium spp.)

Background: Color patterns in angiosperm flowers are produced by spatially and temporally restricted deposition of pigments. Identifying the mechanisms responsible for restricted pigment deposition is a topic of broad interest. Some dicots species develop bicolor petals, which are often caused by the post-transcriptional gene silencing (PTGS) of chalcone synthase (CHS) genes. An Asiatic hybrid lily (Lilium spp.) cultivar Lollypop develops bicolor tepals with pigmented tips and white bases. Here, we analyzed the global transcription of pigmented and non-pigmented tepal parts from Lollypop, to determine the main transcriptomic differences. Results: De novo assembly of RNA-seq data yielded 49,239 contigs (39,426 unigenes), which included a variety of novel transcripts, such as those involved in flavonoid-glycosylation and sequestration and in regulation of anthocyanin biosynthesis. Additionally, 1258 of the unigenes exhibited significantly differential expression between the tepal parts (false discovery rates 2-fold higher in the pigmented parts. Thus, LhMYB12 should be involved in the transcriptional regulation of the biosynthesis genes in bicolor tepals. Other factors that potentially suppress or enhance the expression of anthocyanin biosynthesis genes, including a WD40 gene, were identified, and their involvement in bicolor development is discussed. Conclusions: Our results indicate that the bicolor trait of Lollypop tepals is caused by the transcriptional regulation of anthocyanin biosynthesis genes and that the transcription profile of LhMYB12 provides a clue for elucidating the mechanisms of the trait. The tepal transcriptome constructed in this study will accelerate investigations of the genetic controls of anthocyanin color patterns, including the bicolor patterns, of Lilium spp

白山におけるアキノキリンソウとミヤマアキノキリンソウのリボゾーム遺伝子座とRAPD分析

[論文] Articl

細胞・組織培養由来イネの遺伝学的解析

京都大学0048新制・論文博士博士(農学)乙第9605号論農博第2139号新制||農||746(附属図書館)学位論文||H9||N3063(農学部図書室)16497UT51-97-H442(主査)教授 遠藤 隆, 教授 大西 近江, 教授 池橋 宏学位規則第4条第2項該当Doctor of Agricultural ScienceKyoto UniversityDA

High temperature enhances anthocyanin coloration in Asiatic hybrid lily flowers via upregulation of the MYB12 positive regulator

Although high atmospheric temperatures suppress anthocyanin accumulation in most plant species, we show that high temperatures accel-erate anthocyanin pigmentation in flower tepals of Asiatic hybrid lilies (Lilium spp.). After incubation at high temperatures (35 degrees C) for two days, anthocyanin color became deeper in the most of tepal parts of two Asiatic hybrid lily cultivars, although the basal parts of 'Montreux' tepals and top parts of 'Toronto' outer tepals were whitened. Environmental stimuli often affect the expression of R2R3-MYB positive regulators that control anthocyanin biosynthesis. Although their expression is often suppressed by hot temperatures in other species, the expression of lily MYB12 in tepals was upregulated by high temperatures. MicroRNA828 (miR828), which suppresses the action of MYB12 post-transcriptionally, exhibited reduced accumulation levels under high temperature, indicating that miR828 regulation is involved in MYB12 upregulation. In ad-dition, transcription levels of MYB12, estimated by unspliced MYB12 transcript accumulation, were also activated by high temperatures. Thus, both suppressed miR828 accumulation and increased MYB12 transcription are likely to be involved in MYB12 activation at high temperatures. In the whitened basal parts of 'Montreux' tepals at 35 degrees C, expression of bHLH2 was severely suppressed while that of MYB12 was not affected. The present results demonstrate that plants display diverse responses to hot climatic conditions and shed new light on anthocyanin regulation under various environmental conditions

MicroRNA828/MYB12 Module Mediated Bicolor Flower Development in Lilium dauricum

The lily MYB12 gene, a positive regulator of anthocyanin biosynthesis, is targeted by microRNA828 (miR828). In bicolor tepals of Asiatic hybrid lilies with white lower halves and pigmented upper halves, accumulation levels of miR828 are higher in the lower halves than in the upper halves, and action of MYB12 is suppressed in the lower halves, resulting in bicolor tepal development. This is a newly identified mechanism of color pattern development in flowers. However, which wild species has donated the miR828-mediated bicolor tepal traits to these hybrid lilies is uncertain, and whether miR828-dependent pattern development occurs in species other than Lilium and is responsible for other types of color patterns is unknown. In this study, miR828 accumulation levels were compared between anthocyanin pigmented and unpigmented regions of flowers in lilies and other species. Lilium dauricum is among the parental wild species of Asiatic hybrid lilies. Lilium dauricum showed bicolor tepals, in which anthocyanins highly accumulated in the upper halves, and miR828 accumulation was more than 10 times higher in the lower halves than in the upper halves. Thus, the profile of miR828 accumulation was similar to that found in bicolor cultivars of Asiatic hybrid lilies. It is possible that the miR828-mediated bicolor tepal trait in Asiatic hybrid lilies is derived from L. dauricum. In L. cernuum var. album and an Oriental hybrid lily ???Dizzy???, the suppression of MYB12 expression causes unpigmented tepals or tepal regions, but the unpigmented regions are spatially different from those in bicolor tepals of Asiatic hybrid lilies. MiR828 accumulation levels were similar between white and pink flowers of L. cernuum, and rather higher in pigmented regions than white regions of ???Dizzy??? tepals, suggesting little involvement of miR828 in MYB12 expression suppression. MiR828 accumulation levels were evaluated in bicolor flowers of cherry sage, tulip, and Alstroemeria, but differences in miR828 accumulation were not detected between red and white petal/tepal regions, indicating that the mechanisms by which the bicolor flowers developed in these species are likely different from that occurring in Asiatic hybrid lilies and L. dauricum. Thus, the miR828/R2R3-MYB module is likely responsible for color only in lily flowers and only for the color pattern that consists of lower un-pigmented and upper pigmented regions

The MicroRNA828/MYB12 Module Mediates Bicolor Pattern Development in Asiatic Hybrid Lily (Lilium spp.) Flowers

Some Asiatic hybrid lily cultivars develop bicolor tepals, which consist of anthocyanin-pigmented upper halves and un-pigmented lower halves. MYB12, a subgroup 6 member of R2R3-MYB that positively regulates anthocyanin biosynthesis, is downregulated in the lower halves. However, MYB12 is usually expressed over entire tepal regions in numerous lily cultivars. Why MYB12 of bicolor cultivars exhibits variable expression spatially in a single tepal remains unclear. Since the lily MYB12 mRNA harbored a binding site for microRNA828 (miR828), the involvement of miR828 in variable spatial accumulation of MYB12 transcripts was evaluated. We analyzed the cleavage of MYB12 mRNA, mature miR828 accumulation, and MYB12 transcript-derived siRNA generation (microRNA-seq). In the bicolor tepals, mature miR828 was more highly accumulated in the lower halves than in the upper halves, and miR828-directed cleavage of MYB12 transcripts was observed predominantly in the lower halves. Moreover, the cleavage triggered the production of secondary siRNA from MYB12 transcripts, and the siRNAs were accumulated predominantly in the lower halves. Consequently, miR828 suppressed MYB12 transcript accumulation in the white region, and the miR828/MYB12 module participated in the development of bicolor patterns in lily flowers. The results present the first example of a microRNA mediating flower color patterns. Finally, we discuss the potential of miR828 creating flower color variations through suppressing the activity of subgroup 6 R2R3-MYB positive regulators in other species