Sugarcane is cultivated in tropical and subtropical regions where cold stress is not very common, but lower yields and reduced industrial quality of the plants are observed when it occurs. In our efforts to enhance cold tolerance in sugarcane, the gene encoding the enzyme isopentenyltransferase (ipt) under control of the cold inducible gene promoter AtCOR15a was transferred via biolistic transformation into sugarcane (Saccharum spp.) cv. RB855536. Semiquantitative RT-PCR using GAPDH encoding glyceraldehyde-3-phosphate dehydrogenase as the normalizer gene showed the increased expression of the ipt gene under cold stress. The detached leaves of genetically modified plants subjected to low temperatures showed visible reduction of leaf senescence in comparison to non-transgenic control plants. Induced overexpression of ipt gene also enhanced cold tolerance of non-acclimated whole plants. After being subjected to freezing temperature, leaf total chlorophyll contents of transgenic plants were up to 31 % higher than in wild type plants. Also, lower malondialdehyde content and electrolyte leakage indicated less damage induced by cold in transgenic plants. Thus, the expression of ipt driven by the stress inducible COR15a promoter did not affect plant growth while providing a greater tolerance to cold stress.
Losses in sugarcane crops due to water deficiencies have been increasing in Brazil and worldwide. NPK1 (Nicotiana protein kinase1) is naturally found in tobacco plants and provides tolerance to cold, heat, and salt stress, with positive results in corn, tobacco, and Arabidopsis. This study aimed to evaluate the development and productivity of transgenic sugarcane with the insertion of the tobacco NPK1 gene. Sugarcane plants cv. RB855536 were genetically transformed with the insertion of the NPK1 gene by biolistic (transgenic event obtained by biolistic) and agrobacteria (transgenic event obtained by Agrobacterium infection). These transgenic sugarcane plants were evaluated in relation to the control (non-genetically transformed sugarcane plants). The growth and productivity of the plants were evaluated in a greenhouse, at four periods: 60, 120, 180, and 270 days after planting (DAP). The measurements recorded included the average number, length, and diameter of the stems, number of green leaves, leaf area, and leaf area index. The fresh stalk mass was evaluated at 270 DAP. The insertion of the gene NPK1 significantly contributed to sugarcane development. There was a significant difference improvement on tillering across all the evaluated periods. At the end of the cycle, plants transformed using the Agrobacterium maintained a higher number of tillers, with 68 % more tillers than the other plants (control and biolistic). The fresh stalk mass was 48 % higher in productivity (than the control and biolistic). Transgenic sugarcane did not show any delay or decrease in growth compared to the conventional non-transformed sugarcane. Therefore, the results suggest that the insertion of the NPK1 gene into sugarcane is a promising alternative for increasing crop productivity
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