SUPERVISOR: Christian LUSCHNIG

PROJECT ASSIGNED TO: Linh TA THI THUY

Plants are sessile organisms that evolved highly adjustable growth patterns to allow for their adaptation to different environmental conditions. Especially, plants developed numerous strategies to sense and respond to their environment by adjusting morphogenesis in general, and by modulating directional organ growth (tropisms) in particular. Gravitropism, the directional growth response relative to the orientation of the gravity vector, is a key factor in determining the final architecture of the plant. Such directional growth responses are mediated by the transient, asymmetric distribution of auxin within plant tissues, a process controlled by directional, polar auxin transport. Canonical PIN-FORMED (PIN) auxin transport proteins mediate such polar transport, as a consequence of their asymmetric localization at the plasma membrane (PM). Recent work identified the Arabidopsis WAVY GROWTH3 (WAV3) and WAV3 HOMOLOG (WAVH) RING-finger ubiquitin E3 ligases as important regulators of root gravitropism, via control of PIN polarity. Specifically, a loss of WAV3/WAVH causes a shift in PIN protein distribution, exhibiting basal instead of apical localization. However, the mechanisms of WAV3/WAVH-PIN crosstalk are unknown. To answer this question, we employ a proximity biotin labeling approach to identify proteins interacting with WAV3. Confirmed interacting proteins will then be characterized in detail, as they likely represent elements of signaling cascades required for PIN polarity control. With the functional characterization of such WAV3-dependent pathways, we should reveal important new insights into mechanisms of plant adaptation even under stressful environmental conditions.

Figure 1. Comparison of wild type (w.t.), wav triple (wtrp) and wav triple XVE»Ven:WAV3 directional root growth. Agravitropic root growth of wav triple is rescued by induced expression of Ven:WAV3.

Figure 2. Loss of WAV3/WAVH genes causes an apical-to-basal polarity switch in PIN2 localization in root meristem cells (white arrowheads).