Seminars

Much of the adult growth of plants could be viewed as a type of behavioral movement to explore and exploit a heterogeneous environment. In animals, movement of one part of an organism is often coordinated with movement of distant appendages, such as compensatory muscle movements. How does the plant coordinate its molecular and morphological responses in one part of its body to adjust or compensate to responses in another part of its body, all without a central nervous system? We have used the split root system in Arabidopsis to examine the conditional response of each side of two isolated root systems in the same plant at both the morphological and whole transcriptome level. The results show that the plant can "flip" its normal response to nitrogen (or lack of) at both the morphological and transcriptome level depending on conditions in the isolated root system. This behavior can be modeled as a decision tree in which the plant integrates different sources of information to mount a strategy to gather a limiting nutrient and minimize unproductive growth. Decapitation experiments show that communication between isolated root systems is mediated by the shoot and mutant analysis shows cytokinin signaling controls crosstalk in one direction but not the other. These results lead to a simple model by which the plant can make sophisticated "decisions" to shape its overall body plan and long-term movements without a central processor based on integrating a local and a systemic signal.