On microbes and plants: New insights in phytohormonal research

Alterations to the biological activities of phytohormones can result in modifications of plant physiological and developmental processes. Microbial organisms that are pathogens or symbionts of plants are natural models for studying such modifications. Several genes of bacterial origin able to alter phytohormone content and activity in plants have been characterized, including genes whose products can synthesize and modify phytohormones and/or hydrolyze phytohormone conjugates. Their expression in transgenic plants has confirmed that several morphological and physiological traits can be altered simultaneously by the expression of a single gene. This approach has been shown to be of value not only in achieving a better understanding of the fundamental mechanisms underlying growth and development in plants, but also in attaining agriculturally important goals, such as the control of ripening.