Oxidative stress response in sugarcane

Abstract

Oxidative stress response in plants is still poorly understood in comparison with the correspondent phenomenon in bacteria, yeast and mammals. For instance, nitric oxide is assumed to play various roles in plants although no nitric oxide synthase gene has yet been isolated. This research reports the results of a search of the sugarcane expressed sequence tag (SUCEST) database for homologous sequences involved in the oxidative stress response. I have not found any gene similar to nitric oxide synthase in the SUCEST database although an alternative pathway for nitric oxide synthesis was proposed. I have also found several genes involved in antioxidant defense, e.g. metal chelators, low molecular weight compounds, antioxidant enzymes and repair systems. Ascorbate (vitamin C) is a key antioxidant in plants because it reaches high concentrations in cells and is a substrate for ascorbate peroxidase, an enzyme that I found in different isoforms in the SUCEST database. I also found many enzymes involved in the biosynthesis of low molecular weight antioxidants, which may be potential targets for genetic manipulation. The engineering of plants for increased vitamin C and E production may lead to improvements in the nutritional value and stress tolerance of sugarcane. The components of the antioxidant defense system interact and their synthesis is probably closely regulated. Transcription factors involved in regulation of the oxidative stress response in bacteria, yeast and mammals differ considerably among themselves and when I used them to search the SUCEST database only genes with weak similarities were found, suggesting that these transcription regulators are not very conserved. The involvement of reactive oxygen species and antioxidants in plant defense against pathogens is also discussed.<br>A resposta ao estresse oxidativo não é bem conhecida em plantas como em bactérias, leveduras e humanos. Por exemplo, assume-se que óxido nítrico tem várias funções em plantas apesar do gene que codificaria para óxido nítrico sintetase nunca ter sido isolado. Este trabalho descreve os resultados de uma busca no banco de dados de seqüências expressas de cana de açúcar (SUCEST) de genes envolvidos na resposta ao estresse oxidativo. Eu não encontrei genes similares a óxido nítrico no banco de dados do SUCEST, mas uma via alternativa para a produção deste radical livre pode ser proposta. Eu também encontrei vários genes envolvidos na defesa antioxidante, como quelantes de metais, antioxidantes de baixo peso molecular, enzimas antioxidantes e sistemas de reparo. Ascorbato (vitamina C) é um importante antioxidante em plantas porque é encontrado em altas concentrações em células vegetais e porque é substrato de ascorbato peroxidase, uma enzima que eu encontrei em diferentes isoformas no banco de dados do SUCEST. Eu também encontrei várias enzimas envolvidas na biossíntese de antioxidantes de baixo peso molecular que podem ser alvos para manipulação genética. A obtenção de plantas modificadas geneticamente que sintetizariam vitaminas C e E...

O3 Sensitivity in a Potential C4 Bioenergy Crop: Sugarcane in California

“…This could be exploited by selection in conventional breeding programs or by more modern techniques, including molecular marker‐assisted selection (Nogueira et al, 2003; Casu et al, 2005). Using expressed sequence tags, for example, a number of antioxidant metabolite systems have been identified in sugarcane (Sorares‐Netto, 2001; Souza et al, 2001).…”

Sensitivity of Gas Exchange Parameters to Ozone in Diverse C4 Sugarcane Hybrids

“…Development of resistance to O 3 and to other stresses (e.g., Boyer, 1982) in sugarcane and energy canes would contribute substantially to providing a sustainable source of biofuel feedstock (USDOE, 2007;Houghton et al, 2006). Resistance to chilling and water stress are associated with resistance to oxidant stress (Ort, 2001) and a number of antioxidant metabolite systems have been identifi ed in Saccharum (Soares-Netto, 2001;Souza et al, 2001). Antioxidant capacity has been linked to high fi ber content among Saccharum clones, and both are likely linked to the genomic contribution of S. spontaneum.…”

“…A meta‐analysis of reproductive impacts of O 3 (Leisner and Ainsworth, 2011) found that in exposures to O 3 above 70 nmol mol −1 , fruit weight was less sensitive in maize than in C 3 plants, although most reproductive parameters were equally inhibited in C 3 and C 4 plants. Ozone exposure stimulated induction of cellular antioxidants in maize to the same extent as in C 3 plants (Ruzsa et al, 1999), although the protective impact on growth and carbon assimilation is unknown. The previous result of substantial sensitivity to O 3 in C 4 sugarcane (Grantz and Vu, 2009) was not expected.…”

Defense-related proteins involved in sugarcane responses to biotic stress

“…A search in the SUCEST database found catalases with similarities to the three maize isoforms (CAT 1, CAT 2 and CAT 3) ( Soares Netto, 2001 ). The level of gene expression for a catalase isoform (CAT3) increases after infection with G. diazotrophicus (2.5-fold), Herbaspirillum rubrisubalbicans (5-fold) ( Lambais, 2001 ) and S. scitamineum ( Lao et al , 2008 ).…”