Animal Anti–Apoptotic Genes Enhance Recovery from Drought Stress in Tobacco

The anti–apoptotic nematode CED–9 gene and a 3’ non–coding mRNA region of the human Bcl–2 gene, referred to as 161–1, enhanced resistance to drought and recovery after re–watering in transgenic Nicotiana tabacum L. CV Glurk plants. The effect of drought on plant functions was investigated by withholding water from pots for 6, 8, 10 and 13 days. Results showed that controls and transgenic tobacco did not differ among each other under well–watered conditions. Differences appeared however, on day 3 of water deprivation, where controls exhibited a significantly steeper decline in photosynthesis (A) compared to the transgenic lines. On day 10 of drought stress, losses due to respiration exceeded gains from photosynthesis in Glurk and G115 (vector control), but not in CED–9 and 161–1. Stomatal conductance (gs) was generally higher in the transgenic when compared to controls, and there were no differences between controls and transgenic tobacco in relative water content. Significant differences were found among lines recovering after 13 days of water deprivation. CED–9 and 161–1 exhibited significantly higher values of A on day 17 than controls. Recovery of controls was significantly affected after prolonged periods of water stress; 84 and 82% of leaves in 161–1 and CED–9 recovered from drought, comparing to 70 and 67% in Glurk and G115, respectively. The most notable differences were observed in the number of plants flowering after re– watering, where 67% of 161–1 plants flowered compared to 33 and 30% of CED–9 and G115, respectively. Glurk had the lowest number of plants recovering, with only 17% of its individuals flowering after re–watering.