Cell wall pectins and arabinogalactan proteins (AGPs) are important for pollen tube growth. In this study, immunoblot profiling analyses combined with immunocytochemical techniques were used to analyze the temporal and spatial dynamics of four pectin and two AGP epitopes in the olive pollen during in vitro germination. All pectin and AGP epitopes increased their levels during germination. In the mature pollen, galactans localized in the cytoplasm of the vegetative cell, the pollen wall, and the apertural intine. After gennination, bgalactans localized in the pollen tube wall, particularly at the tip, and formed a collar-like structure around the germinative aperture. Arabinans were mainly present in the pollen tube cell wall, forming ring-shaped deposits at regular intervals in the subapical zone. As expected, the pollen tu be wall was rich in highly methyl-esterified pectins at the apex, while the cell wall mainly contained desesterified pectins in the shank. The wall of the generative cell was labeled with arabinans, highly methyl-esterified homogalacturonans and JIM13 epi topes. In addition, the extracelular material coating the outer oxine layer was rich in arabinans, desesterificd pectins and JIM 13 epitopcs. Our results show that pectins and AGPs are newly synthesized in the pollen tu be during pollen germination, being their synthesis and secretion temporally and spatially regulated. We suggest that galactans might provide mechanical stability to the pollen tube, reinforcing those regions that are particularly sensitive to tension stress and/or mechanical damage. On the other hand, arabinans and AGPs might be important in recognition and adhesion phenomena of the pollen tube and the stylar transmitting cclls, as well as the egg and sperm cells.

This work was funded by ERDF-cofinanced project AGL2008-00517/AGR (MCINN) and P06-AOR-o1791 (Junta de Andlucia). KZ and AZ thank the CSIC for providing JAE DOCgrants.

Resumen del póster presentado al Pollen Congress, celebrado en Madrid (España) del 17 al 20 de septiembre de 2013.

Peer reviewed