ABSTRACT
9-cis-epoxycarotenoid dioxygenase (NCED) encodes a key enzyme in abscisic acid (ABA) biosynthesis. Little is known regarding the regulation of stress response by NCEDs at physiological levels. In the present study, we generated transgenic tobacco overexpressing an NCED3 ortholog from citrus (CsNCED3) and investigated its relevance in the regulation of drought stress tolerance. Wild-type (WT) and transgenic plants were grown under greenhouse conditions and subjected to drought stress for 10 days. Leaf predawn water potential (Ψwleaf), stomatal conductance (gs), net photosynthetic rate (A), transpiration rate (E), instantaneous (A/E) and intrinsic (A/gs) water use efficiency (WUE), and in situ hydrogen peroxide (H2O2) and abscisic acid (ABA) production were determined in leaves of irrigated and drought-stressed plants. The Ψwleaf decreased throughout the drought stress period in both WT and transgenic plants, but was restored after re-watering. No significant differences were observed in gs between WT and transgenic plants under normal conditions. However, the transgenic plants showed a decreased (P ≤ 0.01) gs on the 4th day of drought stress, which remained lower (P ≤ 0.001) than the WT until the end of the drought stress. The A and E levels in the transgenic plants were similar to those in WT; therefore, they exhibited increased A/gs under drought conditions. No significant differences in A, E, and gs values were observed between the WT and transgenic plants after re-watering. The transgenic plants had lower H2O2 and higher ABA than the WT under drought conditions. Our results support the involvement of CsNCED3 in drought avoidance.
Subject(s)
Dioxygenases/biosynthesis , Nicotiana/physiology , Plant Proteins/biosynthesis , Abscisic Acid/biosynthesis , Adaptation, Physiological , Citrus/enzymology , Citrus/genetics , Dioxygenases/genetics , Dioxygenases/metabolism , Droughts , Plant Leaves/enzymology , Plant Leaves/metabolism , Plant Proteins/genetics , Plant Proteins/metabolism , Plants, Genetically Modified/metabolism , Stress, Physiological , Nicotiana/enzymology , Nicotiana/genetics , Nicotiana/metabolismABSTRACT
O objetivo do presente trabalho foi caracterizar os aspectos morfológicos e agronômicos de três acessos de jambu (Spilanthes oleracea L.) nas condições do Norte de Minas Gerais. O estudo foi desenvolvido em casa de vegetação, no período de abril a junho de 2009, no Instituto de Ciências Agrárias da Universidade Federal de Minas Gerais (ICA/UFMG), localizado na cidade de Montes Claros, Minas Gerais, Brasil. O delineamento experimental foi o inteiramente casualizado, com três tratamentos e oito repetições. Os tratamentos foram os acessos de jambu (1- Montes Claros/MG; 2- Pará, Norte do Brasil; 3- Cristália/MG). Dois meses após o transplantio, foram avaliados o comprimento da inflorescência (cm), o comprimento e a largura das folhas do terceiro nó de cada planta (cm) e a matéria fresca e seca da parte aérea e das inflorescências (g). Foram também caracterizadas a coloração dos caules e os tipos de inflorescências. A cor dos caules foi distinguida visualmente, variando de roxo intenso, acessos de Cristália e Montes Claros, a verde claro, acesso do estado do Pará. Os subtipos de inflorescência foram caracterizadas como simples ou geminadas e alongadas ou globóides. Observou-se que o acesso de Jambu, proveniente do estado do Pará, apresentou os melhores resultados para a maioria das características avaliadas. Esse acesso apresentou inflorescências dos tipos simples alongada,e, ocasionalmente, geminadas, tanto globóides como alongadas, enquanto os acessos de Cristália e Montes Claros apresentaram inflorescências simples globóides. Pode-se concluir que os três acessos são equivalentes comercialmente. Entretanto, para produção de sementes, recomenda-se o cultivo do acesso de jambu proveniente do estado do Pará.
The aim of this study was to characterize morphological and agronomic aspects of three Jambu (Spilanthes oleracea L.) accessions under the conditions of North Minas Gerais State, Brazil. The study was carried out in a greenhouse from April to June 2009 in the Institute for Agrarian Sciences of Federal University of Minas Gerais (ICA/UFMG), located in the city of Montes Claros, Minas Gerais, Brazil. The experimental design was completely randomized, with three treatments and eight replicates. Treatments were Jambu accessions (1- from Montes Claros City, Minas Gerais; 2- from Pará State, North of Brazil; 3- from Cristália City, Minas Gerais). Two months after transplanting, the inflorescence length (cm), the length and width of leaves of the third node of each plant (cm) and the fresh and dry matter of shoot and inflorescences (g) were assessed. The color of stems and the type of inflorescences were also characterized. Stem color was visually distinguished, varying from intense purple, Cristália and Montes Claros accessions, to light green, Pará State accession. Inflorescence subtypes were characterized as simple or geminated and elongated or globoid. Jambu accession from Pará State presented the best results for most assessed characteristics. This accession presented elongated simple and, occasionally, both globoid and elongated geminated inflorescences, while Cristália and Montes Claros accessions presented globoid simple inflorescences. It can be concluded that all three accessions are commercially equivalent. However, for seed production, cultivation of Jambu accession from Pará State is recommended.
