Interspecific Gene Transfer (Implications for Broadening Temperature Characteristics of Plant Metabolic Processes)

We report here an approach to metabolic engineering to alter the temperature characteristics of an enzyme pool based on the concept of thermal kinetics windows (TKWs), a useful indicator of enzyme performance. A chimeric cucumber NADH-hydroxypyruvate reductase (HPR) gene under the control of a cauliflower mosaic virus 35S promoter was constructed and introduced into the genome of tobacco (Tobacum tobacum). The root system of the R1 generation of the resultant transgenic plants expresses only the cucumber enzyme (the native tobacco HPR gene is light regulated and only found in the aerial portions of the plant). Enzyme isolated from the transgenic root tissues exhibits a TKW centered at 32.5[deg]C, characteristic of cucumber. The pool of HPR in the shoots, containing both tobacco and cucumber enzymes, exhibits a broad TKW consistent with an equal mix of the two forms. These data do not simply demonstrate that an introduced gene can be expressed in a transgenic plant but that the kinetics properties of the resultant enzyme are unaltered and when sufficient enzyme is produced the temperature characteristics of the total pool are altered. This suggests that the temperature characteristics of plant biochemical pathways can be broadened to suit changing thermal environments.