Adrián Gonzalo
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adriangonzalo.bsky.social
Adrián Gonzalo
@adriangonzalo.bsky.social
200 followers 190 following 16 posts
Treasuring exceptions at IJPB (INRAE Versailles). Thirsty for genetics, chromosome biology and evolution.
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adriangonzalo.bsky.social
Check out the Views & News piece that Joiselle Fernandes and I wrote for @nature.com on the recent work from @amarques.bsky.social and colleagues about one of the most bizarre ways to do meiosis rdcu.be/euabu.

Explained for non-experts!
Diagram of two types of reproduction based on their meiosis. A. shows typical meiosis taking place in individuals with two copies of each chromosome (diploids) resulting in both male and female gametes carrying one copy of each chromosome. Fertilization restores the double copy for each chromosome. B. shows Canina meiosis in individuals carrying five copies of each chromosome (pentaploids) where male gametes only carry one copy of each chromosome and female gametes carry four copies of each chromosome. Fertilization restores the five copy for each chromosome.
July 1, 2025 at 10:27 AM
adriangonzalo.bsky.social
Conclusion: we found synapsis dynamics is severely compromised in neo-tetraploids, while in established ones it is more efficient even than diploids, and hybrids display sub-optimal synapsis. The extent of these synapsis defects is correlated with the degree of meiotic instability. 8/8.
A schematic timeline of synapsis completion using HEI10 dynamics as a “developmental clock”. In diploids, there is still some extensive asynapsis at the onset of HEI10 accumulation that quickly declines and synapsis completes as HEI10 accumulates. In neo-tetraploids there is extensive asynapsis, regardless of how advanced HEI10 accumulation is. In hybrids (cross between neo- and established tetraploid), the progression seems similar to that of diploids, but often fails to complete synapsis at the end of the process. Established tetraploids, show the most efficient dynamics, as very little asynapsis is left when HEI10 accumulation begins.
May 9, 2025 at 6:33 PM
adriangonzalo.bsky.social
So, why is it so bad for NEO-4X to have incomplete synapsis? We don’t know but we observed certain (non-linear, probably complex) correlation between the extent of asynapsis and crossover number. Excess of crossovers, we know, is a problem for polyploid meiosis 7/8.
Plot of crossover number vs extent of asynapsis, R2 = 0.608, P < 0.0001
May 9, 2025 at 6:33 PM
adriangonzalo.bsky.social
But why is synapsis so messed up in NEO-4X? We observed defects compatible with problems during earlier stages: less pre-synaptic co-alignments, and slower dynamics elongation of synapsis initiation sites. 6/8.
May 9, 2025 at 6:33 PM
adriangonzalo.bsky.social
We modeled the initial extent of synapsis, the pace of synapsis completion, and the final extent of asynapsis. This suggested that NEO-4X synapsis progress stalls even before HE10 accumulation begins. In summary: EST-4X > 2X > > HYB-4X >>>>>> NEO-4X. 5/8.
Some examples of meiocytes with different degrees of synapsis completion and different levels of HEI10 accumulation. Plots showing comparisons between A. arenosa genotypes for the initial extent of synapsis, the pace of synapsis completion, and the final extent of asynapsis.
May 9, 2025 at 6:33 PM
adriangonzalo.bsky.social
Are these defects associated with problems in synapsis progression? We used the dynamics of HEI10 as a “developmental clock”: many small foci at early stages, few bright foci in later stages, to measure how early/late is the completion of synapsis (measured by the disappearance of ASY1). 4/8
Using the level of HEI10 accumulation (what % of total signal accumulates at bright foci): The higher is the %, the later in the HEI10 dynamics we are. Using the length of ASY1 signal as a negative proxy for the degree of synapsis completion: The lower the ASY1 length, the closer to synapsis completeness. Plotting HEI10 accumulation level vs ASY1 length show the normal trend: the higher is the HEI10 accumulation level the lower is the ASY1 length. In other words: incomplete synapsis is associated to early stages of HEI10 accumulation, and vice versa; full synapsis is typical when HEI10 accumulation is high. HOWEVER, this is not the case for NEO-4X where there is no real progress of synapsis as HEI10 accumulates.
May 9, 2025 at 6:33 PM
adriangonzalo.bsky.social
We analyzed this in Arabidopsis arenosa diploids (2X), newly induced tetraploids (NEO-4X), natural established tetraploids (EST-4X), and hybrids (EST-4X x NEO-4X), which have different levels of meiotic stability: 2X > EST-4X > HYB-4X >> NEO-4X. 3/8
Quantification of meiotic stability in NEO-4x, EST-4X and HYB-4X through the number of meiotic defects like quadrivalents (groups of four homologs associated by crossovers) and univalents (chromosomes that did not receive crossovers) in metaphase I. The frequency of these defects is correlated with the total number of crossovers (measured as the number of HEI10 foci).
May 9, 2025 at 6:33 PM