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Guard cell‐specific upregulation of sucrose synthase 3 reveals that the role of sucrose in stomatal function is primarily energetic

2015; Wiley; Volume: 209; Issue: 4 Linguagem: Inglês

10.1111/nph.13704

1469-8137

Danilo M. Daloso, Thomas Christopher Rhys Williams, Werner Camargos Antunes, Daniela Pereira Pinheiro, Caroline Müller, Marcelo Loureiro, Alisdair R. Fernie,

Plant responses to water stress

Summary Isoform 3 of sucrose synthase ( SUS3 ) is highly expressed in guard cells; however, the precise function of SUS 3 in this cell type remains to be elucidated. Here, we characterized transgenic Nicotiana tabacum plants overexpressing SUS3 under the control of the stomatal‐specific KST 1 promoter, and investigated the changes in guard cell metabolism during the dark to light transition. Guard cell‐specific SUS3 overexpression led to increased SUS activity, stomatal aperture, stomatal conductance, transpiration rate, net photosynthetic rate and growth. Although only minor changes were observed in the metabolite profile in whole leaves, an increased fructose level and decreased organic acid levels and sucrose to fructose ratio were observed in guard cells of transgenic lines. Furthermore, guard cell sucrose content was lower during light‐induced stomatal opening. In a complementary approach, we incubated guard cell‐enriched epidermal fragments in 13 C‐Na HCO 3 and followed the redistribution of label during dark to light transitions; this revealed increased labeling in metabolites of, or associated with, the tricarboxylic acid cycle. The results suggest that sucrose breakdown is a mechanism to provide substrate for the provision of organic acids for respiration, and imply that manipulation of guard cell metabolism may represent an effective strategy for plant growth improvement.