SEMINAR: Plant Biology Research Seminar

The bud is a dynamic organ that defines the lifecycle of perennial plants, enabling cycles of growth and quiescence in synchrony with a seasonal climate. Grapevine is a typical example we study in our lab. An embryonic shoot develops continuously within the buds from early spring, but in a repressed state we call quiescence. Removing the repressor, such as the shoot tip, leads to outgrowth. Text books tell us that the mature buds harden and become dormant in late autumn, whereby repression is no longer external, but internal. Overcoming that repression is classically thought to result from environmental exposure to chilling, which accumulates during winter, just in time for bud burst to repeat the cycle. Although it’s a nice model, this kind of black or white definition doesn’t hold up in the field, as orchardists or arborists will know. In the face of a warming climate, we need a much better understanding of the dynamics of bud quiescence and dormancy, and the seasonal signals that drive normal or disorderly growth. Over the past few years we’ve probed the physiological state of the bud throughout the year in the field and controlled environments. New data show that dormancy per se is a developmental process, which reaches a peak of repression in late summer and is substantially relieved well-before winter. We’ve extending this to study respiratory control, the cell cycle and spatial patterns of oxygen and reactive oxygen species (ROS) in three climates, from temperate/Mediterranean to subtropical. The disparity in seasonal coordination of these processes between climates gives keen insight to the disorderly production system in subtropical viticulture, and potential consequences of a warmer climate. To further understand the role of oxygen and ROS signalling in bud development, we investigated the acute phase of bud burst in controlled conditions. This reveals a coordinated spatial pattern of ROS associated with vascular activation early during bud burst. We have a number of additional studies in progress, to spatially model oxygen fluxes during bud dormancy, and to define the intercellular and inter-organ signalling that governs this system.