Half-reserve Mitosis of Sibling Nuclei in Gymnosporangium asiaticum

Abstract

Fluorescent DAPI (4',6-diamidino-2-phenylindole) dyeing showed that Gymnosporangium asiaticum (Miyabe ex Yamada) was dikaryotic both in teliospore and basidiospore is different from other rust fungi, and two pathways of nuclei mitosis in basidiospores are found. Directly germinating produces dikaryotic tubes with appressorium at the tip, while indirectly germinating produces secondary basidiospores in 3 pathways. The first, the daughter nucleus disintegrates before the other one takes mitosis in the secondary spore. The second pathway is with one daughter nucleus disintegrated before another one taking mitosis in the mother basidiospore, then the two newborn nuclei moved into the secondary spore. The third pathway is 3 nuclei co-existing with one of daughter nucleus taking mitosis and another one keeping static in the mother basidiospore. Remains of nucleus at the sterigmatal initial can be found by fluorescence microscope, which demonstrates that one of the daughter nucleus disintegrated actually before secondary basidiospore matured. Artificially inoculations on host chaenomeles show that secondary basidiospores induce stronger pathogenesis than that of basidiospores. Pycniospores are mono-nucleate. Aeciospores with double cells wall are dikaryotic, and a dikaryotic hypha cell exists between every two bi-nucleus aecium spores. One cofferdam layer is found under the pycnium, and aecium is formed only after hapha has passed through this layer. Somatic cells of mycelium in Sabina chinensis are multiple-karyotic, however, in Chaenomeles lagenaria are throughout monokaryotic. In the life cycle of G. asiaticum, half of two daughter nuclei is valid for new cell born, even haploid basidiospores produce secondary spore abiding by this rule, the daughter nuclei must be dispelled before the secondary spore matured.

Multinuclei Occurred Under Cryopreservation and Enhanced the Pathogenicity of Melampsora larici-populina

“…Germ tubes of the urediniospores of M. larici-populina fuse on the surface of the poplar leaves and form multinucleate cells (Yu et al, 2009), but the vegetative hyphae typically become dikaryotic hyphae when the multinucleate cells develop into infected hyphae. The dikaryon hyphae do not grow with clamp connections, and a sister nucleus in vegetative hyphae is copied in a "half-reserve" manner, with one disappearing or becoming retained and the other flowing into a new cell and remaining as a dikaryon through mitosis (Yu et al, 2017). When the basidiospores regerminate, binucleate secondary basidiospores are formed and can more easily infect the host (Yu et al, 2009).…”