Intracellular organization of the pre-mRNA splicing machinery during Hyacinthus orientalis L. pollen development

Abstract

Spatial organization of splicing machinery elements in metabolically and functionally different pollen cells during Hyacinthus orientalis pollen grain development was examined by localization of trimethylguanosine (TMG) snRNA and Sm proteins, representing splicing small nuclear ribonucleoproteins, as well as SR splicing factors was investigated. In young pollen grains the level of all labeled antigens was the highest displaying essentially uniform distribution in the vegetative and generative nucleus. In the polarized microspore, as well as in the vegetative cell of the young pollen grain, both TMG snRNA and Sm proteins were also found highly concentrated in Cajal bodies. After detachment of the generative cell from the sporoderm, the redistribution of splicing machinery elements into speckled-shape clusters was observed in both nuclei in the pollen. In the mature pollen grain, labeled antigens were still present, both in the vegetative and the generative nucleus. The results reflected that in differentiating H. orientalis pollen cells, the intracellular organization pre-mRNA splicing machinery undergoes significant and characteristic changes during the course of pollen grain development. Changes in the distribution of spliceosomal components relate to the transcriptional activity of both pollen cells during their maturation.