POLLEN EXINE DEVELOPMENT PRECEDES MICROTUBULE REARRANGEMENT IN VIGNA-UNGUICULATA (FABACEAE) - A MODEL FOR POLLEN WALL PATTERNING

Although patterns on pollen exines are highly conserved, heritable traits, there is no prevailing explanation for control of pattern development. In Vigna unguiculata (Fabaceae), the exine reticulum is unusually coarse so that development of the reticulum can be followed by light microscopy. Developing exine patterns were compared with the arrangement of microtubules in the microspore using immunofluorescence labeling of microtubules. Exine pattern developed in microspores at stages with a regular microtubule pattern. At later stages of exine formation, microtubules were arranged in patches under the lumina of the reticulum. We conclude that microtubules do not determine exine pattern. The developing exine appears to rearrange microtubules. We interpret this as evidence for the self-patterning of exine based on intrinsic properties of the matrix between the microspore and the callose wall.