Occurrence and cytological mechanism of numerically unreduced pollen in diploid Populus euphratica

Abstract

Unreduced gametes are the driving force for the polyploidizaiton of plants in nature, and are also an important tool for breeding of triploid individuals. The final heterozygosity of a 2n pollen grain depends on the cytological mechanism behind 2n pollen formation. In this study, meiotic abnormalities were analysed using fluorescent chromosome staining and indirect immunofluorescence during the microsporogenesis of 18 genotypes of diploid P. euphratica Oliv. (2n = 2x = 38). Among the 18 genotypes, 16 genotypes produce 2n pollen and two genotypes produce only normal n pollen. In all 2n pollen producers, we found that the first meiotic division was normal but that the second division was characterized by frequent abnormal spindle orientation (parallel, tripolar, and fused spindles) and premature cytokinesis. The parallel, fused spindles and premature cytokinesis were considered to be leading dyad formation, and tripolar spindles seemed to be causing triad formation at the tetrad stage. There was a higher frequency of parallel spindles than other spindle forms, but no significant correlations between parallel spindles and dyads were observed. However, a significant association (r = 0.68, P < 0.05) between the tripolar spindles and dyads was found. In some Microspore mother cells (MMCs), an indirect immunofluorescence examination of meiosis II revealed that the parallel spindles led to the gathering of one or two non-sister groups of chromosomes, causing an incorporation of RMSs from two daughter nuclei. Therefore, the incorporated RMSs established two nuclear cytoplasmic domains for the control of division plane, resulting in either triad or dyad formation.

High temperature exposure did not affect induced 2n pollen viability in Populus

“…Pollen samples were collected and stored in glass bottles containing allochronic silica gel. We estimated the occurrence rate of 2n pollen with the same methods as Zhang and Kang (2013). The diameters of 500-700 pollen grains were measured per sample.…”

Colchicine induced manifestation of abnormal male meiosis and 2n pollen in Trachyspermum ammi (L.) Sprague (Apiaceae)

“…The parallel spindles resulted in two FDR 2n pollens while fused spindles are accountable to form a dyad and then two FDR 2n pollens. The tripolar spindles develop a mother cell to produce one FDR 2n pollen and two 1n pollen (Zhang and Kang 2013).…”

High Temperature-induced Spindle Destabilization Results in Aborted Pollen Production in Populus

“…The fresh anthers were randomly sampled from the control group and treatment groups and xed in 4% paraformaldehyde (PEM buffer, pH 6.9) for 60 min. Next, α-tubulin immunolocalization analysis of PMCs during meiosis was performed as described previously 19 . Photomicrographs of developing microsporocytes (characterized by different meiotic stages) were collected with a Leica TCS-SP8 confocal laser scanning microscope.…”