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Doctoral Thesis
DOI
https://doi.org/10.11606/T.11.2019.tde-20191220-122301
Document
Author
Full name
Francine Lorena Cuquel
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
Piracicaba, 2000
Supervisor
Title in Portuguese
Senescência foliar e deficiência nutricional em plantas transgênicas de Petunia x hybrida contendo os genes PSAG12-kn1 e PSAG12-ipt
Keywords in Portuguese
DEFICIÊNCIAS NUTRICIONAIS DE PLANTAS
EXPRESSÃO GÊNICA
PETÚNIA TRANSGÊNICA
SENESCÊNCIA FOLIAR
Abstract in Portuguese
Esta pesquisa avaliou o gene “homeobox” knotted-1 (kn1), um gene mutante de milho, o qual acredita-se estar envolvido no metabolismo de citocinina e o gene isopentenil transferase (ipt), um gene bacteriano, que codifica a primeira enzima envolvida na síntese de citocinina. Duas gerações de plantas de Petunia x hybrida contendo o gene PSAG12-kn1 foram induzidas à senescência e avaliadas quanto ao processo de senescência foliar. Este processo foi retardado em vários graus, obtendo-se plantas com fenótipos de não-senescente até nunca senescente. A avaliação da segunda geração mostrou que o promotor SAG12 nem sempre apresentou regulação completa. A expressão do gene kn1 bloqueou o processo de senescência foliar e causou alterações morfológicas e fisiológicas de intensidade moderada a severa. A maioria das plantas não-senescentes apresentaram alterações fenotípicas moderadas, as quais não foram consideradas prejudiciais na avaliação do desempenho das plantas. A avaliação dos dados sugere que o gene kn1 possivelmente afeta direta ou indiretamente o metabolismo da citocinina. Porém, o mecanismo pelo qual o gene kn1 afeta o metabolismo da citocinina ainda está por ser elucidado. Plantas de Petunia x hybrida contendo o gene PSAG12-ipt, quando cultivadas sob deficiência nutricional, apresentaram melhor desempenho horticultural que plantas do tipo selvagem. Sob adequada disponibilidade de nutrientes, o promotor SAG12 não apresentou regulação completa e a expressão do gene ipt causou alterações morfológicas e fisiológicas.
Title in English
Leaf senescence and nutritional deficiency in transgenic Petunia x hybrida plants containing the PSAG12-kn1 and PSAG12-ipt genes
Abstract in English
This research focused on the homeobox knotted-1 gene (knl), a mutant maize gene that is thought to be involved in cytokinin metabolism, and the isopentenyl transferase gene (ipt), a bacterial gene encoding an enzyme that catalyzes the rate-limiting step in cytokinin biosynthesis. Transgenic PSAG12-kn1 Petunia x hybrid plants were subjected to drought stress treatment, and the leaf senescence process was evaluated in two generations. This process was delayed in several degrees from a non-senescent to a never-senescent phenotype. The evaluation of the second progeny generation showed that the promoter SAG12 did not always present complete regulation. Kn1 gene expression blocked the leaf senescence process and caused some morphological and physiological alterations, which ranged from mild to severe intensity. The majority of the plants with a non-senescent phenotype showed mild-alterations, which were not considered detrimental to the plants performances. The data presented support the possibility that the kn1 gene affects cytokinin metabolism either direct or indirectly. The mechanism(s) through the kn1 gene affects the cytokinin metabolism remains to be elucidated. Transgenic PSAG12-ipt Petunia x hybrid plants grown under nutritional deficiency showed better horticultural performance than wild-type plants. Under adequate nutrient supply the SAG12 promoter did not present complete regulation and some ipt gene expression occurred causing morphological and physiological alterations. The ipt gene "leaky" expression under adequate nutritional supply might be attributed to the summer heat-stress during the crop production.
 
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Publishing Date
2019-12-20
 
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