Overlapping pathways of sugars and hormones in control of plant architecture

ABSTRACT:

Plants show enormous plasticity in their shoot and root architecture. Shoot branching is thereby a major modulator of shoot architecture and tightly regulated by different signals involving hormones and nutrients, which interact with each other to fine-tune this developmental process. Growing shoot tips can maintain dominance over the growth of axillary buds in a process termed apical dominance. One mechanism by which the shoot tip acts to prevent the growth of axillary buds is by diverting sugars away from the buds, with sucrose being both necessary and sufficient to induce bud release. Sugars can induce bud outgrowth via different sugar signalling pathways involving HEXOKINASE1 and the sucrose-specific signalling molecule trehalose 6-phosphate (Tre6P). The plant hormone strigolactone also plays a crucial role in shoot branching regulation by inhibiting axillary bud outgrowth. Sugar availability antagonized the effect of strigolactone on bud outgrowth via inhibition of strigolactone signalling which is likely regulated by trehalose 6-phosphate. Interestingly, the regulation of lateral root growth by Tre6P seems to be opposite to its role in shoot branching. While high Tre6P can induce shoot branching only in the presence of strigolactone signalling, high Tre6P inhibits root growth independently of the strigolactone pathway. These results provide compelling evidence that Tre6P is a major player in regulation of plant architecture, and offer the first insights into how Tre6P-signalling is integrated with hormonal and other signalling pathways.

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Fichtner, F, Barbier, FF, Kerr, S, Dudley, C, Cubas, P, Turnbull, C, Brewer, P, and Beveridge, CA (2022). Plasticity of bud outgrowth varies at cauline and rosette nodes in Arabidopsis thaliana. Plant Physiology 188(3): 1586-1603.

Barbier, F, Cao, D, Fichtner, F, Weiste, C, Perez-Garcia, M-D, Caradeuc, M, Le gourrierec, J, Sakr, S, and Beveridge, CA (2021). HEXOKINASE1 signalling promotes shoot branching and interacts with cytokinin and strigolactone pathways. New Phytologist 231: 1088-1104.