2018 ASHS Annual Conference

Control of shoot architecture is a fundamental aspect of plant growth and development. The dissection of molecular mechanisms controlling architecture is important for understanding the basic biological question of ‘how plants grow’ while also having potential agro-economic impacts. Manipulation of shoot architecture allows plants to acquire sufficient levels and quality of light. Variation in the architecture of fruit trees can improve fruit quality and size as well as potentially reducing the cost of training, production, and orchard maintenance. Recently, a mutation in the uncharacterized and highly conserved WEEP gene was identified as the cause of a downward growing (weeping) growth habit in peach, implicating WEEP in the control of lateral shoot growth in trees. Here, we begin to elucidate the molecular mechanism of WEEP and its effect on branch growth. weep branches were subjected to a 4-point bending test, which demonstrated similar structural properties as standard peach branches, rejecting the hypothesis that the downward-growing weeping growth habit results from weak or ‘floppy’ branches. Histological and wood chemistry analyses were conducted to determine how changes in the cell wall could lead to alteration of branch growth habit. However, no obvious differences between weep and standard peach in the quantity or distribution of cell wall polymers were observed. Fiber cells of weep were found to be slightly shorter than those of standard peach, suggesting a role for WEEP in cell elongation. To investigate biochemical roles of WEEP, we have developed a specific antibody to this protein and are currently investigating its subcellular localization, expression pattern, and are using co-immunoprecipitation to discover interacting protein partners. This characterization will aid in understanding molecular function and pathways of WEEP and how this protein contributes to the control of lateral shoot architecture in trees.