Inheritance of garden rose architecture and its association with flowering behaviour

International audienceUnderstanding the genetic basis of plant architecture is limited for woody plants due to the challenges of assessing the inheritance of their complex architecture. We aimed to evaluate the genetic variability of plant form and stature in a garden rose population, analyse the inheritance of plant architecture and its linkage with flowering behaviour and identify the quantitative trait loci (QTLs) controlling garden rose architecture. A total of 98 F 1 hybrids were derived from the cross between two diploid roses, The Fairy (TF) and Rosa × wichurana (RW) that differed in stature and flowering behaviour. The TF exhibits continuous flowering (CF) and has erect stature. The RW is once flowering (OF) and prostrate in stature. Three clones per genotype were multiplied, and a total of 300 plants were cultivated in a field. Flowering behaviour, plant form, plant height, stem diameter and internode length were scored during each of 2&nbsp;years. All architectural traits had significant genetic variances (29–61&nbsp;% of their respective phenotypic variances), and their broad-sense heritability estimates were 0.76–0.92. The majority of CF progeny was erect, whereas the OF progeny was prostrate, suggesting a linkage between plant form and flowering behaviour. The QTL analysis identified eight major QTLs controlling architectural traits. Several candidate genes involved in gibberellin biosynthesis and auxin signalling were identified in the vicinity of the QTLs. High heritability estimates obtained for garden rose architecture indicated that architectural characteristics are feasible targets of rose breeding. Linkage of plant form and flowering behaviour, however, prevents independent selection of these traits. The candidate genes identified can be good targets for future physiological studies.</p

The <it>Vitis vinifera </it>sugar transporter gene family: phylogenetic overview and macroarray expression profiling

<p>Abstract</p> <p>Background</p> <p>In higher plants, sugars are not only nutrients but also important signal molecules. They are distributed through the plant <it>via </it>sugar transporters, which are involved not only in sugar long-distance transport <it>via </it>the loading and the unloading of the conducting complex, but also in sugar allocation into source and sink cells. The availability of the recently released grapevine genome sequence offers the opportunity to identify sucrose and monosaccharide transporter gene families in a woody species and to compare them with those of the herbaceous <it>Arabidopsis thaliana </it>using a phylogenetic analysis.</p> <p>Results</p> <p>In grapevine, one of the most economically important fruit crop in the world, it appeared that sucrose and monosaccharide transporter genes are present in 4 and 59 loci, respectively and that the monosaccharide transporter family can be divided into 7 subfamilies. Phylogenetic analysis of protein sequences has indicated that orthologs exist between <it>Vitis </it>and <it>Arabidospis</it>. A search for <it>cis</it>-regulatory elements in the promoter sequences of the most characterized transporter gene families (sucrose, hexoses and polyols transporters), has revealed that some of them might probably be regulated by sugars. To profile several genes simultaneously, we created a macroarray bearing cDNA fragments specific to 20 sugar transporter genes. This macroarray analysis has revealed that two hexose (<it>VvHT1</it>, <it>VvHT3</it>), one polyol (<it>VvPMT5</it>) and one sucrose (<it>VvSUC27</it>) transporter genes, are highly expressed in most vegetative organs. The expression of one hexose transporter (<it>VvHT2</it>) and two tonoplastic monosaccharide transporter (<it>VvTMT1</it>, <it>VvTMT2</it>) genes are regulated during berry development. Finally, three putative hexose transporter genes show a preferential organ specificity being highly expressed in seeds (<it>VvHT3</it>, <it>VvHT5</it>), in roots (<it>VvHT2</it>) or in mature leaves (<it>VvHT5</it>).</p> <p>Conclusions</p> <p>This study provides an exhaustive survey of sugar transporter genes in <it>Vitis vinifera </it>and revealed that sugar transporter gene families in this woody plant are strongly comparable to those of herbaceous species. Dedicated macroarrays have provided a <it>Vitis </it>sugar transporter genes expression profiling, which will likely contribute to understand their physiological functions in plant and berry development. The present results might also have a significant impact on our knowledge on plant sugar transporters.</p

The Continuous Flowering Gene in Rose Is a Floral Inhibitor

International audienceIn rose, RoKSN, a TFL1 homologue, is a key regulator of continuous flowering. To study the function of this gene in planta, protocols of plant transformation are needed. We complemented tfl1 Arabidopsis mutants and ectopically expressed RoKSN in a continuous-flowering rose. In Arabidopsis, RoKSN complemented the tfl1 mutant by rescuing late flowering and indeterminate growth. In continuous-flowering rose, the ectopic expression of RoKSN led to the absence of flowering. In these transgenic roses, a study of genes implied in the floral regulation was carried out. The floral activator transcripts decreased whereas the FD transcription factor is up-regulated. We conclude that RoKSN is a floral repressor and could regulate the expression of transcripts as RoFT and RoFD. These results could strengthen a mechanism of competitive interactions of RoFT and RoKSN with a common partner, FD to move towards flowering or vegetative developments

Characterization of AgMaT2, a Plasma Membrane Mannitol Transporter from Celery, Expressed in Phloem Cells, Including Phloem Parenchyma Cells[OA]

A second mannitol transporter, AgMaT2, was identified in celery (Apium graveolens L. var. dulce), a species that synthesizes and transports mannitol. This transporter was successfully expressed in two different heterologous expression systems: baker's yeast (Saccharomyces cerevisiae) cells and tobacco (Nicotiana tabacum) plants (a non-mannitol-producing species). Data indicated that AgMaT2 works as an H+/mannitol cotransporter with a weak selectivity toward other polyol molecules. When expressed in tobacco, AgMaT2 decreased the sensitivity to the mannitol-secreting pathogenic fungi Alternaria longipes, suggesting a role for polyol transporters in defense mechanisms. In celery, in situ hybridization showed that AgMaT2 was expressed in the phloem of leaflets, petioles from young and mature leaves, floral stems, and roots. In the phloem of petioles and leaflets, AgMaT2, as localized with specific antibodies, was present in the plasma membrane of three ontologically related cell types: sieve elements, companion cells, and phloem parenchyma cells. These new data are discussed in relation to the physiological role of AgMaT2 in regulating mannitol fluxes in celery petioles

Posttranscriptional Regulation of RhBRC1 (Rosa hybrida BRANCHED1) in Response to Sugars is Mediated via its Own 3′ Untranslated Region, with a Potential Role of RhPUF4 (Pumilio RNA-Binding Protein Family)

The shoot branching pattern is a determining phenotypic trait throughout plant development. During shoot branching, BRANCHED1 (BRC1) plays a master regulator role in bud outgrowth, and its transcript levels are regulated by various exogenous and endogenous factors. RhBRC1 (the homologous gene of BRC1 in Rosa hybrida) is a main branching regulator whose posttranscriptional regulation in response to sugar was investigated through its 3 ' UTR. Transformed Rosa calluses containing a construction composed of the CaMV35S promoter, the green fluorescent protein (GFP) reporter gene, and the 3 ' UTR of RhBRC1 (P35S:GFP::3 ' UTRRhBRC1) were obtained and treated with various combinations of sugars and with sugar metabolism effectors. The results showed a major role of the 3 ' UTR of RhBRC1 in response to sugars, involving glycolysis/the tricarboxylic acid cycle (TCA) and the oxidative pentose phosphate pathway (OPPP). In Rosa vegetative buds, sequence analysis of the RhBRC1 3 ' UTR identified six binding motifs specific to the Pumilio/FBF RNA-binding protein family (PUF) and probably involved in posttranscriptional regulation. RhPUF4 was highly expressed in the buds of decapitated plants and in response to sugar availability in in-vitro-cultured buds. RhPUF4 was found to be close to AtPUM2, which encodes an Arabidopsis PUF protein. In addition, sugar-dependent upregulation of RhPUF4 was also found in Rosa calluses. RhPUF4 expression was especially dependent on the OPPP, supporting its role in OPPP-dependent posttranscriptional regulation of RhBRC1. These findings indicate that the 3 ' UTR sequence could be an important target in the molecular regulatory network of RhBRC1 and pave the way for investigating new aspects of RhBRC1 regulation

Blooming and blooming again : what we learn from rose and strawberry

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Biosynthesis of 2-Phenylethanol in Rose Petals Is Linked to the Expression of One Allele of <i>RhPAAS</i>

International audienceFloral scent is one of the most important characters in horticultural plants. Roses (Rosa spp.) have been cultivated for their scent since antiquity. However, probably by selecting for cultivars with long vase life, breeders have lost the fragrant character in many modern roses, especially the ones bred for the cut flower market. The genetic inheritance of scent characters has remained elusive so far. In-depth knowledge of this quantitative trait is thus very much needed to breed more fragrant commercial cultivars. Furthermore, rose hybrids harbor a composite genomic structure, which complexifies quantitative trait studies. To understand rose scent inheritance, we characterized a segregating population from two diploid cultivars, Rosa × hybrida cv H190 and Rosa wichurana, which have contrasting scent profiles. Several quantitative trait loci for the major volatile compounds in this progeny were identified. One among these loci contributing to the production of 2-phenylethanol, responsible for the characteristic odor of rose, was found to be colocalized with a candidate gene belonging to the 2-phenylethanol biosynthesis pathway: the PHENYLACETALDEHYDE SYNTHASE gene RhPAAS. An in-depth allele-specific expression analysis in the progeny demonstrated that only one allele was highly expressed and was responsible for the production of 2-phenylethanol. Unexpectedly, its expression was found to start early during flower development, before the production of the volatile 2-phenylethanol, leading to the accumulation of glycosylated compounds in petals.Analyse des composés du parfum dans une population en ségrégation qui montre que la synthèse du&nbsp;2-phenylethanol est liée à l'expression d'un allèle deu gène de la&nbsp;phenylacetaldehyde synthase dans les pétale

Dark side of the honeymoon: reconstructing the Asian x European rose breeding history through the lens of genomics

International audienceAbstract Roses have a specific symbolic charge in Western cultural heritage, often used as a metaphor for love and romance. Despite its ancient cultivation, the passion for the phenotypic diversity of roses is relatively recent, dating back to the early 19 th century. During that century, the number of rose varieties has increased exponentially from roughly 100 to 8,000, in such a way that this period can be considered as the golden age for rose breeding. To retrace the history of rose breeding in Europe and shed new light on genetic changes during this period, we collected large phenotypic and genetic data from 204 accessions, including botanical roses and varieties bred between 1800 and 1910. We also used whole-genome sequences from 32 accessions as an extra resource. The genetic makeup of roses is remarkably consistent with a temporal shift from a historical European to a near-Asian genetic background within a few generations. Our analyses are consistent with a substantial erosion of the genetic diversity during this period, both because of the greater contribution of the Asian genepool - a less genetically diverse group - and of specific genomic footprints of selection, in particular regarding the extension of the blooming period. Thanks to this study, we have generated the largest GWAS catalog for roses to date, which can be used as a tool for future rose breeding programs. We particularly discuss the crucial importance of preserving ancient rose collections to safeguard genetic diversity and ensure a sustainable breeding for the long-term