Sense and antisense expression of plasma membrane aquaporin BnPIP1 from Brassica napus in tobacco and its effects on plant drought resistance

A full-length cDNA fragment encoding plasma membrane aquaporin BnPIP1 from Brassica napus was introduced into tobacco (Nicotiana tabacum) in sense and antisense orientation. Transgenic plants with increased or reduced aquaporin levels were identified and used for physiological analysis. Overexpression of BnPIP1 in transgenic tobacco plants resulted in an increased tolerance to water stress at the whole plant level. Leaf protoplasts from sense lines burst quickly in hypotonic solution and the sense seeds germinated earlier than untransformed control in soil containing 20% PEG. On the other hand, transgenic tobacco plants expressing antisense BnPIP1 showed morphological deformation, developmental delay and decreased tolerance to water stress. The antisense leaf protoplasts remained intact and stable for a longer period of time in hypotonic solution. The germination of seeds from antisense lines was seriously inhibited in soil containing 20% PEG. It was also found that the seeds priming with either 20% PEG or 40 μM ABA could be stimulated for germination under osmotic stress in both sense and antisense lines.