Antagonistic Effect of Sucrose Availability and Auxin on Rosa Axillary Bud Metabolism and Signaling, Based on the Transcriptomics and Metabolomics Analysis

International audienceShoot branching is crucial for successful plant development and plant response to environmental factors. Extensive investigations have revealed the involvement of an intricate regulatory network including hormones and sugars. Recent studies have demonstrated that two major systemic regulators-auxin and sugar-antagonistically regulate plant branching. However, little is known regarding the molecular mechanisms involved in this crosstalk. We carried out two complementary untargeted approaches-RNA-seq and metabolomics-on explant stem buds fed with different concentrations of auxin and sucrose resulting in dormant and non-dormant buds. Buds responded to the combined effect of auxin and sugar by massive reprogramming of the transcriptome and metabolome. The antagonistic effect of sucrose and auxin targeted several important physiological processes, including sink strength, the amino acid metabolism, the sulfate metabolism, ribosome biogenesis, the nucleic acid metabolism, and phytohormone signaling. Further experiments revealed a role of the TOR-kinase signaling pathway in bud outgrowth through at least downregulation of Rosa hybrida BRANCHED1 (RhBRC1). These new findings represent a cornerstone to further investigate the diverse molecular mechanisms that drive the integration of endogenous factors during shoot branching

Sucrose promotes cytokinin synthesis and auxin export during axillary bud outgrowth

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Assessing the impact of environmental factors on plant architecture through an integrative approach

National audiencePlant architecture determines yield, vigour, pathogen resistance of a crop as well as shape and visual quality of plants. Controlling the establishment of plant architecture is therefore a key concern for plant breeders and horticultural growers of field and greenhouse crops. Environmental factors have a strong impact on plant architecture. Better understanding and controlling these factors should allow better mastering cultural practices and increase yield but also reduce the use of chemicals (pesticide and growth retardants). In the case of ornamental crops, this may contribute to better master plant shape and offer the way to create new products. However, the understanding of how the environment modulates plant architecture is still poor and further research is needed. To address this question, ARCH-E (Architecture and Environment) team of the Research Institute on Horticulture and Seeds (IRHS, Angers, France) is developing an integrative research program whereby environmental effects on the establishment of plant architecture are examined from the molecular to the all plant levels. Rosebush is the model plant studied in this program. Architectural analysis is used to describe and objectively discriminate plant shapes (Morel et al., 2009, Chéné et al; 2012) and the impact of environmental factors, such as quantity and quality of light, nitrogen or water restriction or mechanical stimulation on the architectural components is studied (Thélier et al., 2011, Abidi et al; 2012, Morel et al., 2012). Beside, tools to assess plant shape through sensory analysis are developed and used to train panels of assessors to characterize the rosebush visual quality (Boumaza et al; 2010). The more in-depth study of the effect of light on rose architecture is carried on and has revealed that light was essential to bud outgrowth in rose, and that blue or red lights could, each individually, trigger bud burst (Girault et al; 2008). Light was shown to be required to stimulate sugar transport (Henry et al; 2011), sugar metabolism (Girault et al, 2010) and sugar signaling (Rabot et al., 2012) as well as the synthesis of the plant hormone gibberellic acid (Choubane et al ; submitted). On the basis of these researches, functional and structural modeling is undergone to integrate these results and simulate branching in response to the light environment (Bertheloot et al., 2011