A Tale of Two Domains Pushing Lateral Roots

Successful plant organ development depends on well-coordinated intercellular communication between the cells of the organ itself, as well as with surrounding cells. Intercellular signals often move via the symplasmic pathway using plasmodesmata. Intriguingly, brief periods of symplasmic isolation may also be necessary to promote organ differentiation and functionality. Recent findings suggest that symplasmic isolation of a subset of parental root cells and newly forming lateral root primordia (LRPs) plays a vital role in modulating lateral root development and emergence. In this opinion article we discuss how two symplasmic domains may be simultaneously established within an LRP and its overlying cells, and the significance of plasmodesmata in this process. Symplasmic Domains Establish New Boundary of Developing Lateral Root Symplasmic (see Glossary) isolation, via temporary or permanent disconnection of plasmodesmata between neighboring plant cells, can occur during the growth, differentiation, and function of certain plant tissues and organs (reviewed in [1-3]). Some symplasmic domains form permanently, whereas others may form transiently, and they can occur at the level of a single cell, a cluster of cells, tissues, and even organs (Box 1). One of the biggest challenges often faced when searching for and studying novel symplasmic domains is the lack of noninvasive, real-time, in situ methods for measuring cellular connectivity, especially if the domains are small or occur