People

Faculty

Savaldi-Goldstein Sigal , Associate Professor

Phone:  (972)-4-8293413

Building/Auditory:  501

Research Interests

One of the most striking features of multicellular organisms is their ability to coordinate information from the various cell types and tissues comprising a single functional organ unit. Unlike animals, plants produce new organs and adjust their growth throughout their life span. In addition, plant cells are held together by a rigid cell wall and do not migrate. These inherently distinct features demand specialized control mechanisms of the growing tissues, to ensure appropriate organ size and shape. How do different cells manage to grow in synchrony and modulate their growth in response to a changing environment?

Small molecule hormone signalling pathways lie at the heart of this growth control.  Despite dramatic advances in identifying signalling components, understanding of their spatiotemporal activities and how they integrate to coordinate whole-organ growth is just beginning to take form.  Our research focuses on the steroid hormone brassinosteroid (BR) signalling pathway. The BR activity triggers growth of above and below-ground organs, but also inhibits growth.  We are currently seeking to understand how the different cell types decode the BR signal and how this information is interpreted at the organ level.

Using the Arabidopsis thaliana root as a model organ, our studies have demonstrated that the spatial distribution of BR activity is an important fine-tuning determinant of root growth. In certain cell types, BR signaling drives cell elongation and cell proliferation (See Hacham et al., 2011, Development), while in others, it restrains them (See Fridman et al., 2014, Genes and Dev. and Vragović, Sela et al., 2015, PNAS). To uncover the molecular genetic framework underlying the differential developmental programs triggered by BR, we established a precise, high-resolution polyribosome-associated mRNA map of temporal and tissue-specific BR responses in various mutant backgrounds. The opposing effect of the hormone on gene expression in the outer epidermal tissue versus the innermost tissues was clearly demonstrated (Vragović, Sela et al., 2015, PNAS). We revealed that BR activity in the inner tissues buffers the promoting effect of the hormone in the epidermis, thus providing a balanced growth.

In parallel, we investigate whether BR-mediated root growth is modulated by environmental signals. We have found that activity of key downstream BR transcription factors blocks root developmental reprogramming in response to low phosphate availability (See Singh et al., 2014, Plant Physiology). Since soluble phosphate levels in many soils are suboptimal for plant growth and productivity, our findings present new research avenues toward understanding how developmental reprogramming is achieved and potential biotechnological means of improving plant performance.