Developmental pathways underlying sexual differentiation in the U/V sex chromosome system of giant kelp.

In many multicellular organisms, sexual development is not determined by XX/XY or ZW/ZZ systems but by U/V sex chromosomes. In U/V systems, sex determination occurs in the haploid phase, with U chromosomes in females and V chromosomes in males. Here, we explore several male, female, and partially sex-reversed male lines of giant kelp to decipher how U/V sex chromosomes and autosomes initiate male versus female development.

3D chromatin maps of a brown alga reveal U/V sex chromosome spatial organization.

Nuclear three dimensional (3D) folding of chromatin structure has been linked to gene expression regulation and correct developmental programs, but little is known about the 3D architecture of sex chromosomes within the nucleus, and how that impacts their role in sex determination. Here, we determine the sex-specific 3D organization of the model brown alga Ectocarpus chromosomes at 2 kb resolution, by mapping long-range chromosomal interactions using Hi-C coupled with Oxford Nanopore long reads. We report that Ectocarpus interphase chromatin exhibits a non-Rabl conformation, with strong contacts among telomeres and among centromeres, which feature centromere-specific LTR retrotransposons.

Methodological notes on gauge invariance in the treatment of waves and oscillations in plasmas via the Einstein-Vlasov-Maxwell system: Fundamental equations.

The theory of gauge transformations in linearized gravitation is investigated. After a brief discussion of the fundamentals of the kinetic theory in curved spacetime, the Einstein-Vlasov-Maxwell (EVM) system of equations in terms of gauge-invariant quantities is established without neglecting the equations of motion associated with the dynamics of the nonradiative components of the metric tensor. The established theory is applied to a noncollisional electron-positron plasma, leading to a dispersion relation for gravitational waves in this model system.