Physiological complexity and plant genetic manipulation

Summary One of the limiting factors in the development of new cultivars in a reasonable time using recombinant DNA techniques, is an inability to predict the interaction between the introgressed gene(s) and the host genome and metabolism.This review presents a survey of the literature on the constraints determining the coherence between alien sequences and their products, and the organization of the receiving genome and its physiological equilibrium. An hypothesis supported by preliminary experimental data is put forward that such constraints derive from coadaptation during the evolution of gene complexes driven by external selection pressure, and by changes in genes coding for key factors of plant metabolism. Conclusions are finally drawn on a series of possible methods to be used in genetic engineering, in relation to breeding practice, compatible with the rules governing the organization of physiological networks.