High endoreduplication after drought-related conditions in haploid but not diploid mosses

Abstract

Background and aims Endoreduplication, the duplication of the nuclear genome without mitosis, is a common process in plants, especially in angiosperms and mosses. Accumulating evidence supports the relationship between endoreduplication and plastic responses to stress factors. Here, we investigated the level of endoreduplication in Ceratodon (Bryophyta), which includes the model organism Ceratodon purpureus. Methods We used flow cytometry to estimate the DNA content of 294 samples from 67 localities and found three well-defined cytotypes, two haploids and one diploid, corresponding the haploids to Ceratodon purpureus and Ceratodon amazonum, and the diploid to Ceratodon conicus, the recombinant between the former two. Key results The endoreduplication index (EI) was significantly different for each cytotype, being higher in the two haploids. In addition, the EI of the haploids was higher during the hot and dry periods typical of the Mediterranean summer than during the spring, whereas the EI of the diploid cytotype did not differ. Conclusions Endopolyploidy may be essential in haploid mosses to buffer periods of drought and to respond rapidly to desiccation events. Our results also suggest that the EI is closely related to the basic ploidy level, and not so much to the nuclear DNA content as previously suggested.

A normalization method that controls for total RNA abundance affects the identification of differentially expressed genes, revealing bias toward morning‐expressed responses

“…However, neither our normalization per tissue nor normalizing per total RNA would fully capture changes in the total RNA per cell that might occur when comparing plants with different cell sizes due to ploidy differences, mutations, or environmental treatments. Endoreduplication can be another challenge in plants, and endoreduplication levels vary between different cell types, and tissues, and in response to different environmental conditions (Pirrello et al, 2018;Wos et al, 2022;Zumel et al, 2023). In these cases, adding spike-ins on a per-cell basis would be optimal, but quantifying cell number is challenging in intact plant tissues.…”