Genetic control of flowering time in woody plants: Roses as an emerging model

Abstract

Genetic control of the timing of flowering in woody plants is complex and has yet to be adequately investigated due to their long life-cycle and difficulties in genetic modification. Studies in Populus, one of the best woody plant models, have revealed a highly conserved genetic network for flowering timing in annuals. However, traits like continuous flowering cannot be addressed with Populus. Roses and strawberries have relatively small, diploid genomes and feature enormous natural variation. With the development of new genetic populations and genomic tools, roses and strawberries have become good models for studying the molecular mechanisms underpinning the regulation of flowering in woody plants. Here, we review findings on the molecular and genetic factors controlling continuous flowering in roses and woodland strawberries. Natural variation at TFL1 orthologous genes in both roses and strawberries seems be the key plausible factor that regulates continuous flowering. However, recent efforts suggest that a two-recessive-loci model may explain the controlling of continuous flowering in roses. We propose that epigenetic factors, including non-coding RNAs or chromatin-related factors, might also play a role. Insights into the genetic control of flowering time variation in roses should benefit the development of new germplasm for woody crops and shed light on the molecular genetic bases for the production and maintenance of plant biodiversity.

De novoassemblies of high-quality reference transcriptomes identifies Rosaceae-common andRosa-specific encoding genes

“…Continuous flowering, fragrance, flower shape, thorn and many traits not presenting in Populus and other woody model plants could be found in roses, hence roses are now becoming a model woody species for understanding the molecular mechanisms regulating these traits [1]. Interestingly, the breeding of modern roses often involves frequent hybridization and polyploidization among species, which often feature stronger diseases resistance and cold resistance, better fragrance and lack of prickles [29-31].…”

“…Later, these assemblies were explored to identify about 8975 transcripts shared by In contrast to the Rosaceae-common transcripts, the Rosa-specific transcripts might be explored to investigate traits specific for roses. Although partial of the domestication processes had been documented [2], the evolutionary history and molecular mechanisms controlling traits special for roses are still not clear [1]. More than half of the 417 transcripts are uncharacterized or without known GO annotation, hence might be related to the phenotypes that have not been characterized in other species.…”

“…However, woody plants represent a large proportion of biodiversity on the earth and harbor many different phenological traits that herbaceous plants do not feature (https://www.worldwildlife.org). One such trait is the continuous flowering behavior of modern roses, an important crop for human beings.Guaranteeing a constant supply of raw materials for cut flowers and related products, continuous flowering becomes one of the most important biological and economical traits for roses [1]. Therefore, the genetic control and related gene-regulatorynetwork for continuous flowering regulation attracts many efforts for many years not only from scientists but also from breeders [1,2].…”

“…One such trait is the continuous flowering behavior of modern roses, an important crop for human beings.Guaranteeing a constant supply of raw materials for cut flowers and related products, continuous flowering becomes one of the most important biological and economical traits for roses [1]. Therefore, the genetic control and related gene-regulatorynetwork for continuous flowering regulation attracts many efforts for many years not only from scientists but also from breeders [1,2]. Currently, RoKSN, the Arabidopsis TFL1-like gene in rose, is the only putative target responsible for continuous flowering [3, 4].Domestication of modern cultivated roses mainly involves hybridization among more than a dozen species [2].…”

“…However, a set of high quality and well-characterized genomic tools/resources are necessary for understanding the biology and domestication of modern roses with more than 30,000 cultivars [8]. Currently, several genetic mapping populations have been developed (see reviews [1,2]) and determination of rose genomes is underway [9]. On the other hand, due to high-level heterozygosity caused very likely by inter-species crossing and polyploidization, achieving an accurate rose genome seems not so easy.Alternatively, a comprehensive gene expression atlas can be constructed with different tissues at different developmental stages.…”