Applied Mathematics Colloquium

Title:  How cells coordinate growth and shape: unravelling the complexity of ion signalling in pollen tubes

Abstract:  Pollen transcriptomics revealed the expression of of about 7.000 genes in pollen, but theoretical modelling suggests that the cooperation of all of these into the processes of wall surface and cytoplasmic volume production is a minimal condition to explain most of the morphogenic events that characterize these cells. Spatial and temporal integration of extended biochemical and biophysical processes is mandatory, and in the past we have proposed that ion dynamics can be a common regulator of fundamental growth processes.

I will report on advances on the biology of Glutamate- Receptor Like (GLR) Ca2+-channels. These channels are hypothesized to participate on the generation of the Ca2+ focused gradient characteristic of functional pollen tubes, and eventually regulate Ca2+ fluxes into other compartments as well. I will present data suggesting an evolutionary conservation of these channels related to a male reproductive function. Further, detailed genetic analysis of GLR family genes, coupled with theoretical analysis of the Ca2+ cytosolic concentration vs. extracellular fluxes, revealed that rather than being strictly plasma membrane channels, they may be differentially distributed throughout the endomembrane system. On the absence of specific peptide tags, we propose that these localizations may be regulated by an underlying mechanism based on specialized sorting chaperone proteins. If this hypothesis is confirmed, the integrated study of of GLRs may start the foundation of a completely new view of Ca2+ signalling and homeostasis in plant cells.