A lion lizard embryo can be made into a female lizard using two different genes — one activated by a sex chromosome and the other activated by high temperatures during development. Sarah Whiteley and Arthur Georges of the University of Canberra published their findings in the journal PLOS Genetics on April 15, 2021.
In many reptiles and fish, the sex of a developing embryo depends on the temperature of the surrounding environment. The phenomenon, known as temperature-dependent sex decisions, was discovered in the 1960s, but despite half a century of in-depth research, scientists have been unable to understand the molecular details of what happened. In a new study, researchers looked at the biochemical pathways needed to make females by studying the phenomenon of lion lizards. Male lion lizards have ZZ chromosomes, while females have ZW chromosomes. However, high temperatures can overturn the ZZ chromosome, causing male lizards to develop into females.
Whiteley and Georges compared the genes of lion lizards with ZW chromosomes to those of ZZ animals exposed to high temperatures. They found that initially, the different developmental genomes of the two female animals were active, but eventually, these pathways came together to produce the ovaries. The findings support recent research that ancient signaling processes within cells help turn high temperatures into gender reversals.
The new study is the first to show that there are two ways to produce ovaries in a lion lizard, bringing us closer to understanding how temperature determines sex. The study also identified several candidate genes that may be involved in temperature-dependent sex decisions. These findings provide the basis for future experiments to understand the role of each gene in perceived temperature and guiding development.
Whiteley added: “The most exciting part of this work is the discovery that the mechanism involves a general and highly conservative epigenetic process of cell processes, signaling pathways, and chromatin modification. This new knowledge brings us closer to understanding how temperature determines gender, so this is a very exciting biological age. ”