Transcriptome analysis of floral bud development and function analysis of a novel CO gene in Paeonia × lemoinei ‘High Noon’

Abstract

Paeonia × lemoinei 'High Noon' is one of the most important cultivars in tree peony (Paeonia sect. Moutan), a traditional horticultural plant in China, with a re-blooming characteristic which was quite different from other cultivars. So, the genetic resources in 'High Noon' were incredibly valuable in flowering-time-modified molecular breeding in tree peony. However, the molecular mechanism underlying the floral bud formation of 'High Noon' was not clear yet. To explore the molecular mechanism in this process, the transcriptomes of three stages during floral bud development were deeply analyzed in this study. As a result, a total of 5816 differentially expressed genes (DEGs) were identified between the three developmental stages, and pathways including ''DNA replication'', ''metabolic pathways'', ''circadian rhythm'', and ''plant hormone signal transduction'' were mostly enriched in the functional enrichment and expression pattern analysis. Furthermore, a total of 584 genes related to the photoperiod pathway were further identified and a novel CO homolog gene PlCO was identified to be a stable hydrophilic protein, which contained both CCT domain and B-box domain. Over-expression of PlCO in Arabidopsis resulted in early flowering, which suggested a promotion role of flowering. The PlCO protein localized in nucleus and possessed a transcription activity ability, which implied that PlCO might function as a transcription factor. The transcriptome analysis revealed pathways involved in floral bud development in tree peony and provided new insight into the regulatory network underlying the floral bud development. The gene identification in 'High Noon' provided new valuable candidate genes for flowering-time-modified molecular breeding in tree peony.

A gibberellin-assisted study of the transcriptional and hormonal changes occurring at floral transition in peach buds (Prunus persica L. Batsch)

“…Besides the activation of GAs biosynthesis and signal transduction pathways shown through the KEGG maps (Additional File 9 ), the correlative network pointed out that GA 4 and GA 7 may control the expression of genes mainly dealing with “ cellular macromolecule biosynthetic process ” and “ generation of precursor metabolites and energy ”, respectively. This finding is in full agreement with data previously discussed and with literature [ 86 – 88 ], focusing on the activation of specific metabolisms once that the bud is transiting into the reproductive phase. We may hypothesize that anticipating this natural peak of GAs through GA 4/7 application at T3 may have triggered this metabolic shift too early, when the bud was still in vegetative phase, thus stimulating the vegetative growth.…”

“…The analysis of DEGs related to bud development pointed out that response to auxin is upregulated at T1 and this is consistent with previous results showing a positive role of this hormone in flowering promotion in several species, among which Arabidopsis [ 82 , 83 ], strawberry [ 84 ], and saffron [ 85 ]. The contrast T3 vs. T5 revealed a generally increasing metabolic activity in terms of polysaccharide and cell wall organization, as well as an enhanced transcriptional activity, which are typical of an actively developing reproductive bud [ 86 – 88 ].…”