Research Progress on Phenotypic Plasticity

Organisms respond to environmental changes through two primary mechanisms: Fleeing or physiological adaptation. For many organisms, the possibilities and opportunities for escape are limited, so they often need to rely on altering physiological functions, behaviors, or phenotypes in response to environmental changes. This phenomenon of organisms developing different phenotypes in response to different environments is phenotypic plasticity. Phenotypic plasticity, the ability to develop different phenotypes in different environments, is a fundamental attribute of organisms and an important way to adapt to the environment. The robustness of biological systems to genetic variation and environmental disturbances is referred to as canalization. Canalization enables organisms to buffer various internal or external perturbations, helping to maintain the stability of crucial traits and reflecting different strategies for organisms to adapt to environmental changes. Bradshaw's 1965 proposition initiated the study of phenotypic plasticity's evolutionary genetic basis, leading to contemporary research focusing on methodologies and technologies for its assessment. Nowadays, phenotypic plasticity has become a popular research field, and with the development of new methods and technologies, researchers are increasingly focusing on research methodologies related to phenotypic plasticity. For quantitative assessment of phenotypic plasticity, researchers often utilize populations with identical genetic backgrounds and quantify plastic responses in two or more different environments, including a control environment. Classic methods for quantifying phenotypic plasticity compare differences in phenotype values at the population or individual level or examine the regression slope of phenotype values against the environment. Classic quantification methods have limitations, especially with nonlinear reactions. For instance, when reaction norm is nonlinear, simplifying it through responses to only two environments may make it challenging to accurately quantify plasticity, leading to potential serious underestimation or overestimation. Current research aims to refine methodologies, considering genetic backgrounds, gene-environment interactions (GxE), and other factors. Phenotypic plasticity is shaped by genetic and epigenetic factors. However, many details remain unclear, and future research needs to integrate genetic maps, transcriptomics, metabolomics, proteomics and epigenomics methods to reveal relevant mechanisms and principles. The relationship between phenotypic plasticity and adaptability varies across scenarios, requiring case-specific examination. Costs and constraints associated with plasticity must be considered when evaluating adaptability. Accurately assessing the costs of plastic responses can provide important insights into understanding the adaptability of plastic responses. Furthermore, the interpretation of plasticity responses may vary with researchers' perspectives and focuses, highlighting the necessity for more accurate definitions and descriptions of plasticity. With advancements in genomics, phenomics, single-cell biology and other fields, multidisciplinary research is becoming the norm. This systematic review provides a concise overview of phenotypic plasticity, including historical evolution, mechanisms, quantification methodologies, and its relationship with adaptability. Using examples from animals, plants, and microorganisms, it highlights challenges and proposes future research directions for a comprehensive understanding of this phenomenon across organisms.