The genetics of sex determination in stinging nettle (Urtica dioica)

Nettle, a Long-Known Fiber Plant with New Perspectives

The stinging nettle Urticadioica L. is a perennial crop with low fertilizer and pesticide requirements, well adapted to a wide range of environmental conditions. It has been successfully grown in most European climatic zones while also promoting local flora and fauna diversity. The cultivation of nettle could help meet the strong increase in demand for raw materials based on plant fibers as a substitute for artificial fibers in sectors as diverse as the textile and automotive industries. In the present review, we present a historical perspective of selection, harvest, and fiber processing features where the state of the art of nettle varietal selection is detailed. A synthesis of the general knowledge about its biology, adaptability, and genetics constituents, highlighting gaps in our current knowledge on interactions with other organisms, is provided. We further addressed cultivation and processing features, putting a special emphasis on harvesting systems and fiber extraction processes to improve fiber yield and quality. Various uses in industrial processes and notably for the restoration of marginal lands and avenues of future research on this high-value multi-use plant for the global fiber market are described.

Demographic and genetic consequences of disturbed sex determination

During sex determination, genetic and/or environmental factors determine the cascade of processes of gonad development. Many organisms, therefore, have a developmental window in which their sex determination can be sensitive to, for example, unusual temperatures or chemical pollutants. Disturbed environments can distort population sex ratios and may even cause sex reversal in species with genetic sex determination. The resulting genotype-phenotype mismatches can have long-lasting effects on population demography and genetics. I review the theoretical and empirical work in this context and explore in a simple population model the role of the fitness vyy of chromosomally aberrant YY genotypes that are a consequence of environmentally induced feminization. Low vyy is mostly beneficial for population growth. During feminization, low vyy reduces the proportion of genetic males and hence accelerates population growth, especially at low rates of feminization and at high fitness costs of the feminization itself (i.e. when feminization would otherwise not affect population dynamics much). When sex reversal ceases, low vyy mitigates the negative effects of feminization and can even prevent population extinction. Little is known about vyy in natural populations. The available models now need to be parametrized in order to better predict the long-term consequences of disturbed sex determination.This article is part of the themed issue 'Adult sex ratios and reproductive decisions: a critical re-examination of sex differences in human and animal societies'.

Plant Sex Chromosomes

Although individuals in most flowering plant species, and in many haploid plants, have both sex functions, dioecious species-in which individuals have either male or female functions only-are scattered across many taxonomic groups, and many species have genetic sex determination. Among these, some have visibly heteromorphic sex chromosomes, and molecular genetic studies are starting to uncover sex-linked markers in others, showing that they too have fully sex-linked regions that are either too small or are located in chromosomes that are too small to be cytologically detectable from lack of pairing, lack of visible crossovers, or accumulation of heterochromatin. Detailed study is revealing that, like animal sex chromosomes, plant sex-linked regions show evidence for accumulation of repetitive sequences and genetic degeneration. Estimating when recombination stopped confirms the view that many plants have young sex-linked regions, making plants of great interest for studying the timescale of these changes.