A positive feedback loop of LHW-TMO5 and local auxin biosynthesis in vascular development ($) (Plant Cell Physiol)

Proper development of root vascular tissue is necessary for plant growth, as these tissues are responsible for nutrient and water uptake. Multiple key players including transcriptional factors (TF) and hormones are involved in vascular development. In this paper Ohashi-Ito et al. have identified a feedback loop mechanism involving the heterodimer complex LHW (LONESOME HIGHWAY, a bHLH TF) – TMO5 (TARGET OF MONOPTEROS 5) and auxin biosynthesis. The auxin biosynthesis occurs via a two-step pathway catalyzed by enzymes YUCCA (YUC) and TAA. YUC4 expression in the root apical meristem regulates local auxin biosynthesis and is downstream of LHW-TMO5. The loss of function mutant yuc4 has reduced auxin levels and fewer cambium cells in the root vasculature. On the other hand, the expression levels of LHW and TMO5 are reduced in the yuc4 mutant suggesting a possible feedback loop through which auxin regulates root vascular cell differentiation. (Summary by Suresh Damodaran) Plant Cell Physiol. 10.1093/pcp/pcz156