Chromosome number, sex determination, and meiotic chromosome behavior in the praying mantid Hierodula membranacea - PubMed (original) (raw)
Chromosome number, sex determination, and meiotic chromosome behavior in the praying mantid Hierodula membranacea
Leocadia V Paliulis et al. PLoS One. 2022.
Abstract
Praying mantids are important models for studying a wide range of chromosome behaviors, yet few species of mantids have been characterized chromosomally. Here we show that the praying mantid Hierodula membranacea has a chromosome number of 2n = 27, and X1X1X2X2 (female): X1X2Y (male) sex determination. In male meiosis I, the X1, X2, and Y chromosomes of H. membranacea form a sex trivalent, with the Y chromosome associating with one spindle pole and the X1 and X2 chromosomes facing the opposite spindle pole. While it is possible that such a sex trivalent could experience different spindle forces on each side of the trivalent, in H. membranacea the sex trivalent aligns at the spindle equator with all of the autosomes, and then the sex chromosomes separate in anaphase I simultaneously with the autosomes. With this observation, H. membranacea can be used as a model system to study the balance of forces acting on a trivalent during meiosis I and analyze the functional importance of chromosome alignment in metaphase as a preparatory step for subsequent correct chromosome segregation.
Conflict of interest statement
The authors have declared that no competing interests exist.
Figures
Fig 1. Alignment of nucleotides 2170 to 2813 of NC_048984.1 (complete mitochondrial genome sequence of H. membranacea) to MZ571202 (isolate from mantid obtained from US provider) and MZ571203 (isolate from mantid obtained from German provider).
The MZ571202 isolate was 100% identical to the sequence of NC_048984.1, and the MZ571203 isolate varied at one base and therefore was >99% identical.
Fig 2. Aceto-orcein squash of a meiosis I spermatocyte in the praying mantis Hierodula membranacea.
Twelve bivalents and one sex trivalent (highlighted in pink with component sex chromosomes noted) are present in chromosome spreads of this species. Scale bar = 5μm.
Fig 3. Segregation of chromosomes in meiosis I in the praying mantis Hierodula membranacea.
A) Meiosis I spermatocyte with sex trivalent (arrow). The sex trivalent remains aligned on the metaphase plate with the autosomes (0, 6, 12, 22 min). Anaphase begins (24 min) and the Y chromosome (arrowhead) separates from the X1 and X2 chromosomes, which move together to the same spindle pole (arrow—26, 29, 33, 34 min). Scale bar = 10μm. B) Analysis of the positioning of the trivalent and the autosomes at metaphase I. A line was drawn between the estimated spindle poles (white arrows), showing the spindle axis (left panel). A second line was drawn perpendicular to the spindle axis at the midpoint of the line representing the spindle axis. The distances between the edges of the chromosome facing the pole (estimated kinetochore) and the perpendicular line were measured (yellow braces for the trivalent). The ratio of these distances was then calculated in ten spermatocytes (right panel). Similar calculations were made for two autosomes in the same cell (red). C) Graph of position of X2 and Y kinetochores of the trivalent shown in A. The trivalent has a balanced alignment at the center of the spindle, with the Y kinetochore maintaining the same distance from the spindle midline as the X2 kinetochore.
References
- White MJD. The evolution of the sex chromosomes. J Genet. 1941;42:173.
- Hughes-Schrader S. Polarization, kinetochore movements, and bivalent structure in the meiosis of male mantids. Biol Bull. 1943;85:265–300.
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