Estudo da interação entre aveia branca e Meloidogyne incognita: patogenicidade e expressão gênica diferencial
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Data
2018-05-02
Autores
Marini, Patrícia Meiriele
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Meloidogyne incognita é considerado um dos nematoides de maior importância econômica em termos mundiais. Para seu adequado manejo, uma das estratégias mais eficientes é o uso de cultivares resistentes. Portanto, estratégias para otimizar os programas de melhoramento genético são necessárias. A análise de expressão gênica tem ampliado a compreensão dos mecanismos de interação planta-nematoide e acelerado o desenvolvimento de genótipos resistentes. A cultivar de aveia branca IPR Afrodite, resistente a M. incognita, e cultivares suscetíveis foram avaliadas em relação à sua tolerância a este nematoide, além de ter sido estudado o comportamentode genes candidatos que regulam sua resistência, desafiados com densidades populacionais iniciais crescentes de M. incognita, durante o seu estabelecimento e manutenção do parasitismo. Para a avaliação da tolerância, plantas cultivadas em vasos de 3.600 cm3 foram inoculadas com 0,0625 (187,5); 0,125 (375); 0,25 (750); 0,5 (1500); 1 (3000); 2 (6000); 4 (12000); 8 (24000); 16 (48000) e 32 (96000) exemplares por cm3 de solo e avaliadas aos 67 dias após a inoculação (DAI), através da mensuração do desenvolvimento das plantas, além da multiplicação do nematoide. Os resultados mostraram que, em densidades menores, IPR Afrodite apresentou fator de reprodução próximo a 1,0, sugerindo menor expressão da resistência. Em função desses resultados, experimento semelhante foi conduzido para análise da expressão gênica dessa cultivar ao nematoide, com avaliações aos 0 (imediatamente antes da inoculação), 2 e 9 DAI. A partir de reações de RT-qPCR, verificou-se que dois genes (Lrk 14 e LOX) apresentaram regulação em resposta ao nematoide e padrões de regulação diferenciados entre as cultivares. IPR Afrodite apresentou estratégias moleculares contrastantes às observadas em URS Torena, sugerindo-se que há regulação tardia e negativa em URS Torena, enquanto que, em IPR Afrodite, Lrk14 atuou como amplificador de respostas de defesa inicial, prolongando o sinal de ameaça após a detecção inicial do patógeno. O gene que codifica LOX foi desencadeado, como resposta induzida por efetores, o que geralmente resulta em reação de hipersensibilidade, como já observado em trabalhos anteriores envolvendo tal interação.
Meloidogyne incognita is considered one of the main economic important nematodes worldwide. For its management, the use of resistant cultivars is amongst the more efficient strategy. Therefore, strategies to optimize the genetic breeding programs are necessary. The gene expression analysis has amplified the comprehension about the mechanisms involved in the plant-nematode interaction and accelerated the development of resistant genotypes. The oat cultivar IPR Afrodite, resistant to M. incognita, and cultivars suscetibles was evaluated in relation to its tolerance to this nematode and, besides, the behavior of candidate genes regulating the resistance reaction was studied, challenged with crescent initial population densities of M. incognita, during its establishment and parasitism maintenance. To tolerance evaluation, plants cropped in 3,600 cm3 -pots were inoculated with 0,0625 (187,5); 0,125 (375); 0,25 (750); 0,5 (1500); 1 (3000); 2 (6000); 4 (12000); 8 (24000); 16 (48000) e 32 (96000) exemplars.cm-3 of soil and evaluated at 67 days after inoculation (DAI), through the mensuration of the plant development and nematode multiplication. Results showed that, in lower densities, IPR Afrodite showed reproduction factor values closed to 1.0, suggesting a lower resistance expression. In face of these results, a similar experiment was conducted to gene expression analysis of this cultivar to nematode, with evaluations at 0 (immediately before inoculation), 2 and 9 DAI. From RT-qPCR reactions, we could verify that two genes (Lrk and LOX) were regulated in response to nematode and that different regulatory patterns were observed between cultivars. IPR Afrodite showed molecular strategies contrasting to those observed in URS Torena, suggesting a late and negative regulation in URS Torena, while to IPR Afrodite, Lrk14 acted as an amplifier of initial defense responses, prolonging the threat signal after the initial detection of the pathogen. The gene that codifies to LOX was unleashed, as a response induced by effectors, which usually results in a hypersensitive reaction, as observed previously.
Meloidogyne incognita is considered one of the main economic important nematodes worldwide. For its management, the use of resistant cultivars is amongst the more efficient strategy. Therefore, strategies to optimize the genetic breeding programs are necessary. The gene expression analysis has amplified the comprehension about the mechanisms involved in the plant-nematode interaction and accelerated the development of resistant genotypes. The oat cultivar IPR Afrodite, resistant to M. incognita, and cultivars suscetibles was evaluated in relation to its tolerance to this nematode and, besides, the behavior of candidate genes regulating the resistance reaction was studied, challenged with crescent initial population densities of M. incognita, during its establishment and parasitism maintenance. To tolerance evaluation, plants cropped in 3,600 cm3 -pots were inoculated with 0,0625 (187,5); 0,125 (375); 0,25 (750); 0,5 (1500); 1 (3000); 2 (6000); 4 (12000); 8 (24000); 16 (48000) e 32 (96000) exemplars.cm-3 of soil and evaluated at 67 days after inoculation (DAI), through the mensuration of the plant development and nematode multiplication. Results showed that, in lower densities, IPR Afrodite showed reproduction factor values closed to 1.0, suggesting a lower resistance expression. In face of these results, a similar experiment was conducted to gene expression analysis of this cultivar to nematode, with evaluations at 0 (immediately before inoculation), 2 and 9 DAI. From RT-qPCR reactions, we could verify that two genes (Lrk and LOX) were regulated in response to nematode and that different regulatory patterns were observed between cultivars. IPR Afrodite showed molecular strategies contrasting to those observed in URS Torena, suggesting a late and negative regulation in URS Torena, while to IPR Afrodite, Lrk14 acted as an amplifier of initial defense responses, prolonging the threat signal after the initial detection of the pathogen. The gene that codifies to LOX was unleashed, as a response induced by effectors, which usually results in a hypersensitive reaction, as observed previously.
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Palavras-chave
Avena sativa, resistência, tolerância, nematoide de galhas, controle genético, resistance, tolerance, root-knot nematode, genetic control