Abstract
The floral transition is a crucial developmental event, but little is known about the underlying regulatory networks in seasonally and continuously flowering roses. In this study, we compared the genetic basis of flowering in two rose species, Rosa chinensis ‘Old Blush’, which flowers continuously, and R. odorata var. gigantea, which blooms in early spring. Gene ontology (GO) terms related to methylation, light reaction, and starch metabolism were enriched in R. odorata var. gigantea and terms associated with sugar metabolism were enriched in R. chinensis ‘Old Blush’ during the floral transition. A MapMan analysis revealed that genes involved in hormone signaling mediate the floral transition in both taxa. Furthermore, differentially expressed genes (DEGs) involved in vernalization, photoperiod, gibberellin (GA), and starch metabolism pathways converged on integrators, e.g., LFY, AGL24, SOC1, CAL, and COLs, to regulate the floral transition in R. odorata var. gigantea, while DEGs related to photoperiod, sugar metabolism, and GA pathways, including COL16, LFY, AGL11, 6PGDH, GASA4, and BAM, modulated the floral transition in R. chinensis ‘Old Blush.’ Our analysis of the genes underlying the floral transition in roses with different patterns of flowering provides a basis for further functional studies.
Highlights
The floral transition is an important developmental event orchestrated by external and developmental stimuli; for example, photoperiod, vernalization, autonomous, aging, gibberellin (GA), and sugar metabolism pathways[1, 2] interact to activate or inhibit the floral transition via a small set of floral integrators, including FLOWERING LOCUS T (FT), CONSTANS-LIKE (COL), SUPPRESSOR OF OVEREXPRESSION OF CO1 (SOC1), FLOWERING LOCUS C (FLC), and floral meristem identity genes, e.g., LEAFY (LFY), APETALA1 (AP1), AGAMOUS-LIKE (AGL), CAULIFLOWER (CAL), and SEPALLATA (SEP)
DNA modification, methylation, sucrose metabolic process, and the regulation of gene expression, epigenetic were enriched in vegetative meristem (VM)-GIG vs. TM-GIG, while differentially expressed genes (DEGs) in secondary vegetative meristem (SVM)-GIG vs. TM-GIG were related to many processes, including photosynthesis, light reaction, development process, starch metabolic process, carbohydrate transport, and so on
Compared with the Gene ontology (GO) terms in the biological process (BP) category identified for VM-GIG vs. TM-GIG, terms related to starch metabolism were more highly enriched in the SVM-GIG vs. TM-GIG comparison (Fig. 1b,c)
Summary
The floral transition is an important developmental event orchestrated by external and developmental stimuli; for example, photoperiod, vernalization, autonomous, aging, gibberellin (GA), and sugar metabolism pathways[1, 2] interact to activate or inhibit the floral transition via a small set of floral integrators, including FLOWERING LOCUS T (FT), CONSTANS-LIKE (COL), SUPPRESSOR OF OVEREXPRESSION OF CO1 (SOC1), FLOWERING LOCUS C (FLC), and floral meristem identity genes, e.g., LEAFY (LFY), APETALA1 (AP1), AGAMOUS-LIKE (AGL), CAULIFLOWER (CAL), and SEPALLATA (SEP). The floral transition in Arabis alpina is regulated by PERPETUAL FLOWERING 1 (PEP1), an ortholog of A. thaliana FLC, which encodes a MADS-box transcription factor that inhibits the floral transition before the winter; the species can return to vegetative growth after flowering. Orthologs of A. thaliana TFL1 have been identified in Fragaria vesca and continuous flowering (CF) roses[15]. GA plays an activating role in regulating the floral transition in A. thaliana, but GAs are maintained at low levels during the floral transition process in both CF and seasonal roses (OF), and increase after flowering[16]. Wang et al proposed that CF is not a strictly qualitative trait, but a qualitative-quantitative trait[19] These results indicate that floral genes other than RoKSN regulate the rose floral transition
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