Mechanisms and Research Advances of Horizontal Gene Transfer (HGT) in Plants and Microorganisms

It is becoming increasingly clear that horizontal gene transfer (HGT) serves as a key mechanism enabling the movement of genetic material across species during biological evolution. By extending beyond the constraints of vertical inheritance, HGT exerts substantial influence on the formation of biological diversity and ecological adaptation. Recent advances in genomics and phylogenetics have driven significant progress in understanding HGT in both plants and microorganisms. This paper summarizes the primary criteria and identification methods for HGT, including multidimensional assessments such as integration sequence characteristics, codon preference, colinearity patterns, and phylogenetic inconsistencies. Current knowledge of HGT in plants is also synthesized, including its discovery, functional consequences, gene characteristics, and underlying mechanisms, with particular emphasis on its contributions to terrestrial adaptation, metabolic pathway remodeling, and the evolution of stress resistance. In microorganisms, the principal routes of HGT—transformation, transduction, conjugation, and other non-classical modes—are reviewed, along with the ways in which host factors and environmental conditions jointly shape the frequency and direction of gene transfer. Potential mechanisms and evolutionary implications of Maverick/Polinton-like viroids acting as mediators of eukaryotic HGT are also highlighted.