Drought and Salinity Tolerance in Transgenic Potato Expressing the Betaine Aldehyde Dehydrogenase Gene

Abstract

Glycine betaine (GB) is a common compatible solute in many different organisms including higher plants. Many plant species can accumulate GB in response to drought and salinity. GB is synthesized by conversion of choline to GB through a two-step oxidation via the intermadiate betaine aldehyde. In higher plants, the relevant enzymes are choline monooxygenase (CMO) and betaine aldehyde dehydrogenase (BADH). The fact that many important crops, such as rice, potato and tomato are betaine-deficient has inevitably led to the proposal that it might be possible to increase drought and salinity tolerances by genetic engineering of GB synthesis. In the present study, the transgenic plants of potato cultivar Gannongshu 2 were obtained by Agro- bacterium-mediated transformation of the expression vector pBIBB contained BADH gene under the control of the constitutive promoter CaMV 35S. PCR, Southern, and Northern blot analyses showed that the BADH gene was integrated into potato genome, transcribed and expressed in the transgenic plants. The analysis of BADH activity of transgenic plant leaves revealed that the BADH activity ranged from 2.1 to 10.5 U, while it was not detectable in the control plants. There was a negative relationship (y = –3.774x+57.083, r = 0.989**) between BADH activity and relative electric conductivity of the transgenic potato leaves. The trans- genic potato plants grew normally under NaCl and polyethylene glycol (PEG) stresses with increase of 0.41–1.00 cm for plant height and 10–35% for fresh weight per plant compared with the control plants. This result demonstrated that the transgenic potato plants can improve tolerances to drought and salinity as a result of transformation and expression of BADH gene.