From survival to plant productivity mode: cytokinins allow avoiding the evolutionary-oriented avoidance strategy under environmental stress conditions

The evolution of adaptive mechanisms in plants to environmental stresses involves activation of stress avoidance strategy that allows plants escaping the potentially damaging effects of these conditions. The avoidance mechanisms are reflected by reduced vegetative growth, early flowering, accelerated senescence and loss of biomass and yield. However, the survival mode has been also kept in crop plants and constitute an obstacle for improving food production. Survival is not enough for agriculture and must be changed to productivity mode. Breeding programs and genetic engineering have not succeeded to genetically remove these responses probably due to their polygenic nature. Our successful attempts to delay premature plant senescence by autoregulation of cytokinins levels (through IPT induction by a senescence promoter) constitute a technology for developing highly productive plants. Surprisingly, these transgenic plants displayed also high productivity during drought tolerance. Our transcriptomic study indicates that cytokinins act through reverting the survival transcriptional program allowing sustainable plant productivity under stress conditions. Further study related to stress signal transduction in the transgenic plants suggests that cytokinins desensitize environmental stress cues and prevents growth arrest and allow productivity maintenance. We succeeded in improving yield under stressful conditions by removing the premature alarms that trigger growth reduction and assured their survival in evolution. This generic technology has been successfully implemented in major crops. Based on the present transcriptome study, we suggest that cytokinins uncouple the evolutionary-based connection between plant growth and productivity and stress tolerance and offer a novel technology for yield improvement in stressful environments.