Branching out in new directions: the control of root architecture by lateral root formation

Summary Plant roots are required for the acquisition of water and nutrients, for responses to abiotic and biotic signals in the soil, and to anchor the plant in the ground. Controlling plant root architecture is a fundamental part of plant development and evolution, enabling a plant to respond to changing environmental conditions and allowing plants to survive in different ecological niches. Variations in the size, shape and surface area of plant root systems are brought about largely by variations in root branching. Much is known about how root branching is controlled both by intracellular signalling pathays and by environmental signals. Here, we will review this knowledge, with particular emphasis on recent advances in the field that open new and exciting areas of research. Contents Summary 595 I. Background 595 II. Formation of lateral roots 596 III. Endogenous factors regulating the stages of lateral root development 597 IV. Plasticity: modification of lateral root development by the environment 603 V. Transcriptomic studies to identify potential new regulators of lateral root development 608 VI. Conclusions and future challenges 608 Acknowledgements 608 References 609