Spatial division of phosphoenolpyruvate carboxylase and nitrate reductase activity and its regulation by cytokinins in CAM-induced leaves of Guzmania monostachia (Bromeliaceae)

Autor(es)

Pereira, Paula Natalia ^[1] ; Purgatto, Eduardo ^[2] ; Mercier, Helenice ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Biosci, Dept Bot, BR-05508090 Sao Paulo - Brazil

^[2] Univ Sao Paulo, Fac Pharmaceut Sci, Dept Food & Expt Nutr, BR-05422970 Sao Paulo - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Journal of Plant Physiology; v. 170, n. 12, p. 1067-1074, AUG 15 2013.
• Citações Web of Science: 7

Resumo

Crassulacean acid metabolism (CAM) is a physiological adaptation of plants that live in stress environment conditions. A good model of CAM modulation is the epiphytic bromeliad, Guzmania monostachia, which switches between two photosynthetic pathways (C-3-CAM) in response to different environmental conditions, such as light stress and water availability. Along the leaf length a gradient of acidity can be observed when G. monostachia plants are kept under water deficiency. Previous studies showed that the apical portions of the leaves present higher expression of CAM, while the basal regions exhibit lower expression of this photosynthetic pathway. The present study has demonstrated that it is possible to induce the CAM pathway in detached leaves of G. monostachia kept under water deficit for 7 d. Also, it was evaluated whether CAM expression can be modulated in detached leaves of Guzmania and whether some spatial separation between NO3- reduction and CO2 fixation occurs in basal and apical portions of the leaf. In addition, we analyzed the involvement of endogenous cytokinins (free and ribosylated forms) as possible signal modulating both NO3- reduction and CO2 fixation along the leaf blade of this bromeliad. Besides demonstrating a clear spatial and functional separation of carbon and nitrogen metabolism along G. monostachia leaves, the results obtained also indicated a probable negative correlation between endogenous free cytokinins - zeatin (Z) and isopentenyladenine (iP) - concentration and PEPC activity in the apical portions of G. monostachia leaves kept under water deficit. On the other hand, a possible positive correlation between endogenous Z and iP levels and NR activity in basal portions of drought-exposed and control leaves was verified. Together with the observations presented above, results obtained with exogenous cytokinins treatments, strongly suggest that free cytokinins might act as a stimulatory signal involved in NR activity regulation and as a negative regulator of PEPC activity in CAM-induced leaves of G. monostachia during a diel cycle. (C) 2013 Elsevier GmbH. All rights reserved. (AU)

• Processo FAPESP: 10/04273-3 - Divisão espacial da atividade das enzimas PEPC e NR e sua regulação por citocininas em folhas de Guzmania monostachia induzidas ao CAM.
• Beneficiário: Paula Natália Pereira
• Modalidade de apoio: Bolsas no Brasil - Mestrado
• Processo FAPESP: 11/50637-0 - Competência para a expressão do metabolismo ácido das crassuláceas (CAM) em bromélia epífita: sinalização, modulação da expressão, perfil transcricional e interação com o metabolismo de nitrogênio
• Beneficiário: Helenice Mercier
• Modalidade de apoio: Auxílio à Pesquisa - Temático