Differential Expression of Genes Encoding Acid Invertases in Multiple Shoots of Bamboo in Response to Various Phytohormones and Environmental Factors

Abstract

The promoter regions of two cell wall invertase genes, Boβfruct1 and Boβfruct2, and a vacuolar invertase gene, Boβfruct3, in Bambusa oldhamii were cloned, and putative regulatory cis-elements were identified. The expression of these three genes in multiple shoots of bamboo that were cultured in vitro under different conditions was analyzed by real-time PCR. The two cell wall invertase genes were upregulated by indole-3-acetic acid and cytokinins but responded differently to other phytohormones and different temperatures. Boβfruct1 was also upregulated by sucrose and glucose. In contrast, the Boβfruct2 expression was induced by the depletion of sucrose, and this induction could be suppressed by glucose and sucrose. The expression of Boβfruct3 was light-dependent; however, abscisic acid (ABA) could induce its expression in the dark. ABA and light exhibited an additive effect on the expression of Boβfruct3. Our results suggest that these three Boβfruct genes have individual roles in the adaption of the plant to environmental changes. Boβfruct2 might also have an essential role in the immediate response of cells to sucrose availability and in the maintenance of sink activity. Moreover, Boβfruct3 might be one of the interacting nodes of the light and ABA signaling pathways.

Cytokinins Are Initial Targets of Light in the Control of Bud Outgrowth

“…Indeed, sugar supplies were less efficient (as measured by percentage bud outgrowth and bud elongation) than BAP supply. In other developmental systems and species, CKs were shown to adjust the sugar partitioning and sink strength of some organs through the regulation of sugar transporters and invertases (Thomas, 1986;Roitsch and Ehneß, 2000;Guivarc'h et al, 2002, Werner et al, 2008Proels and Roitsch, 2009;Liao et al, 2013). Our results and those previous reports support the model whereby, in adverse light conditions, light through the down-regulation of CK would limit sugar sink strength in bud and thus repress outgrowth.…”

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

“…However, the activity of invertase was partially recovered in tasg1 treated with BAP, suggesting that CKs might regulate the invertase activity involved in sucrose remobilization. Our findings are consistent with previous studies in which CKs were shown to adjust the sugar partitioning and sink strength of some organs through the regulation of sugar transporters and invertases ((Thomas, 1986; Roitsch and Ehneß, 2000; Guivarc’h et al, 2002; Werner et al, 2008; Proels and Roitsch, 2009; Liao et al, 2013). In addition, our results are in agreement with recent results obtained by Roman et al (2016) in rose buds showing that exogenous feeding of CK induces SUC2 and VInv, although an environmental cue— light—was integral to their system.…”

“…CKs have also been shown to induce VInv expression and nutrient sink strength in bamboo and tobacco (Roitsch and Ehneß, 2000; Werner et al, 2008; Liao et al, 2013). We have shown that glucose and fructose, which are the hydrolytic products of sucrose cleavage by VInv, can induce branching (Salam et al, 2017).…”

Asparagine and sugars are both required to sustain secondary axis elongation after bud outgrowth in Rosa hybrida

“…enzyme activity in the vicinity of the outgrowing buds, promoting nutrient sink strength (Liao et al, 2013;Rabot et al, 2012;Roitsch and Ehneß, 2000).…”

“…Nitrate deficiency also significantly reduces photosynthetic rate, leaf area and leaf chlorophyll concentration, and consequently leads to a lower biomass production (Gulmon and Chu, 1981;Zhao et al, 2005). High invertase gene expression and enzyme activity during bud outgrowth are well documented (Liao et al, 2013;Rabot et al, 2012), suggesting that sucrose is used for carbon supply of elongating axes II. Furthermore, Dhont et al (2012) have demonstrated that sucrose, glutamine and arginine contents increase concomitantly in apical outgrowing buds in spruce.…”