RESUMO
The presence of a large central vacuole is one of the hallmarks of a prototypical plant cell, and the multiple functions of this compartment require massive fluxes of molecules across its limiting membrane, the tonoplast. Transport is assumed to be energized by the membrane potential and the proton gradient established by the combined activity of two proton pumps, the vacuolar H(+)-pyrophosphatase (V-PPase) and the vacuolar H(+)-ATPase (V-ATPase). Exactly how labor is divided between these two enzymes has remained elusive. Here, we provide evidence using gain- and loss-of-function approaches that lack of the V-ATPase cannot be compensated for by increased V-PPase activity. Moreover, we show that increased V-ATPase activity during cold acclimation requires the presence of the V-PPase. Most importantly, we demonstrate that a mutant lacking both of these proton pumps is conditionally viable and retains significant vacuolar acidification, pointing to a so far undetected contribution of the trans-Golgi network/early endosome-localized V-ATPase to vacuolar pH.
Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/enzimologia , Genoma de Planta/genética , Pirofosfatase Inorgânica/metabolismo , ATPases Vacuolares Próton-Translocadoras/metabolismo , Vacúolos/enzimologia , Aclimatação , Arabidopsis/citologia , Arabidopsis/genética , Arabidopsis/fisiologia , Proteínas de Arabidopsis/antagonistas & inibidores , Proteínas de Arabidopsis/genética , Temperatura Baixa , Endossomos/enzimologia , Flores/citologia , Flores/enzimologia , Flores/genética , Flores/fisiologia , Concentração de Íons de Hidrogênio , Pirofosfatase Inorgânica/antagonistas & inibidores , Pirofosfatase Inorgânica/genética , Meristema/citologia , Meristema/enzimologia , Meristema/genética , Meristema/fisiologia , Mutagênese Insercional , Fenótipo , Raízes de Plantas/citologia , Raízes de Plantas/enzimologia , Raízes de Plantas/genética , Raízes de Plantas/fisiologia , Plântula/citologia , Plântula/enzimologia , Plântula/genética , Plântula/fisiologia , Análise de Sequência de DNA , ATPases Vacuolares Próton-Translocadoras/antagonistas & inibidores , ATPases Vacuolares Próton-Translocadoras/genética , Rede trans-Golgi/enzimologiaRESUMO
Sulfate uptake and distribution in plants are managed by the differential expression of a family of transporters, developmentally, spatially, and in response to sulfur nutrition. Elucidation of the signaling pathways involved requires a knowledge of the component parts and their interactions. Here, the expression patterns of the full complement of sulfate transporters in wheat, as influenced by development and sulfur nutrition, are described. The 10 wheat sulfate transporters characterized here are compared to the gene families for both rice and Brachypodium, for whom full genome information is available. Expression is reported in young seedlings with a focus on roles in uptake from nutrient solution and differential expression in relation to sulfate deprivation. In addition, patterns of expression in all organs at the grain filling stage are reported and indicate differential responses to nutritional signals of the individual transporters in specific tissues and an overall coordination of uptake, storage, and remobilization to deliver sulfur to the developing grain.