Exploring LOG genes: drivers of prickle evolution in the plant kingdom

Convergent evolution, where unrelated species independently evolve similar traits, provides valuable insights into the genetic and developmental adaptation. In plants, physical defenses like spines, thorns, and prickles exemplifies this phenomenon. These structures, collectively termed "spinescence," arise from distinct developmental origins-spines from leaves, thorns from stems or branches, and prickles as epidermal outgrowths-but converge in function to deter herbivory and enhance survival. Among these, prickles are particularly interesting due to their morphological diversity and repeated gain or loss across various plant lineages. The genus Solanum serve as model for studying prickle genetics. In "Spiny Solanums," prickles evolved approximately six million years ago, with prickle loss occurring multiple times as seen in domesticated eggplant (Solanum melongena). Recent studies identify the LONELY GUY (LOG) gene family, crucial for cytokinin biosynthesis, as a key regulator of prickle development. Loss-of-function mutations in LOG homologs associated with prickleless phenotypes in various plants, including roses, chinese dates, and alfalfa, suggesting a conserved role in prickle suppression. This review explores the evolutionary, genetic, and molecular mechanisms underlying prickle development, emphasizing the LOG gene family. It discusses phenotypic convergence and agriculture applications, such as breeding prickle-free crops, offering broader insights into plant adaptation and the evolution of physical defenses.