Sucrose promotes etiolated stem branching through activation of cytokinin accumulation followed by vacuolar invertase activity

Abstract

16The potato (Solanum tuberosum L.) tuber is a swollen stem. Sprouts growing from the tuber 17 nodes represent dormancy release and loss of apical dominance. We recently identified 18 sucrose as a key player in triggering potato stem branching. To decipher the mechanisms by 19 which sucrose induces stem branching, we investigated the nature of the inducing molecule 20 and the involvement of vacuolar invertase (VInv) and the plant hormone cytokinin (CK) in 21 this process. Sucrose was more efficient at enhancing lateral bud burst and elongation than 22 either of its hexose moieties (glucose and fructose), or a slowly metabolizable analog of 23 sucrose (palatinose). Sucrose feeding induced expression of the sucrose transporter gene 24 SUT2, followed by enhanced expression and activity of VInv in the lateral bud prior to its 25 burst. We observed a reduction in the number of branches on stems of VInv-RNA interference 26 lines during sucrose feeding, suggesting that sucrose breakdown is needed for lateral bud 27 burst. Sucrose feeding led to increased CK content in the lateral bud base prior to bud burst. 28 Inhibition of CK synthesis or perception inhibited the sucrose-induced bud burst, suggesting 29 that sucrose induces stem branching through CK. Together, our results indicate that sucrose 30 is transported to the bud, where it promotes bud burst by inducing CK accumulation and VInv 31 activity. 32 33 34In plants, the growing shoot apex inhibits the outgrowth of axillary buds further down the 35 stem to control the number of branches. This phenomenon is referred to as apical dominance 36

Effects of source-sink regulation and nodal position of the main crop on the sprouting of regenerated buds and grain yield of ratoon rice

“…It was demonstrated that CTK synergistically induces the production of extracellular invertase and hexose transporters, which are functionally coupled to provide carbohydrates to sink tissues and are involved in phloem unloading (Roitsch and Ehne, 2000). It was reported that sugar-induced lateral bud outgrowth was in part, promoted by the induction of CTK-mediated vacuolar invertase activity (Salam et al, 2021). Previous research showed significant differences in stubble dry weight and NSC content at the maturity stage of the main crop under the different leaf-cutting and spikelet-thinning treatments (He et al, 2019).…”

HEXOKINASE1 interferes with cytokinin synthesis and strigolactone perception during sugar-induced shoot branching

“…We previously hypothesized that CK levels are important to promote bud outgrowth when sugars are not readily available for buds (Barbier et al, 2019b). Accordingly, CK has been reported to promote nutrient sink strength (Roitsch & Ehneß, 2000;Werner et al, 2008;Peleg et al, 2011;Wang et al, 2016), and it was recently reported that thus sugarinduced bud outgrowth in dark-grown potato sprouts was mediated, at least partly, by a CK-induced invertase activity (Salam et al, 2020). In this view, we would expect that cytokinin synthesis mutants would indeed have a reduced response to decapitation which enhances sucrose availability.…”

Investigations into the emergent properties of gene-to-phenotype networks across cycles of selection: A case study of shoot branching in plants

“…Axillary buds require a source of sugar to grow out, and the strong demand for sugar by the shoot apex inhibits axillary bud outgrowth (Mason et al, 2014; Barbier et al, 2019). During shoot branching, sugars were reported to promote cytokinin synthesis and inhibit strigolactone perception (Barbier et al, 2019; Bertheloot et al, 2020; Salam et al, 2020; Patil et al, 2021). Despite the detailed knowledge of molecular physiological mechanisms, translating these discoveries into breeding outcomes is still a challenge.…”