Morphological and cytochemical analysis of an unusual nucleus-pyrenoid association in a unicellular red alga

Abstract

Protrusions of the nucleus that extend into the pyrenoid of the unicellular red alga Rhodella maculata have been characterised morphologically and cytochemically. Serial reconstructions indicate that cells frequently have two tubular nuclear protrusions that are up to 1.2 μm long. Cytochemical analyses were undertaken to investigate the nucleic acid content of the protrusions. DNA was not detected in the nuclear protrusions, though clear labelling was seen in all other DNA-containing zones (viz. the main nuclear compartment, the chloroplast and the mitochondria). High concentrations of RNA were observed in the nuclear protrusion. In situ hybridization experiments indicate that ribosomal RNAs..