独脚金内酯与烟素及其信号组分的研究进展OA

Strigolactones(SLs)and karrikins(KARs)are two classes of signaling molecules that share remarkable similarities in their chemical structures and signaling pathways,yet regulate distinct plant growth and developmental processes.SLs represent a novel class of plant hormones,whereas KARs are a class of bioactive small molecules identified in plant-derived smoke that have not yet been detected endogenously in plants.Current research indicates that KARs may mimic an unidentified class of endogenous signaling molecules.SLs and KARs both regulate multiple aspects of plant growth,development,and adaptation to abiotic stress.Regarding their functions,SLs play a key role in regulating shoot branching,whereas KARs play a pivotal role in seed germination and photomorphogenesis.The SL receptor DWARF14(D14)and the KAR receptor KARRIKIN INSENSITIVE 2(KAI2)both belong to the α/β hydrolase family and serve as homologous proteins.They employ a conserved signaling mechanism:upon perceiving SLs or KARs respectively,they recruit the F-box protein MORE AXILLARY GROWTH2(MAX2)to mediate ubiquitination and subsequent degradation of distinct SMAX1 Likes(SMXL)family members for signal transduction,despite exhibiting significant divergence in downstream components.Following ligand perception,both D14 and KAI2 undergo degradation,but through distinct mechanisms:D14 degradation is MAX2-dependent and proteasome-mediated,whereas KAI2 degradation is independent of MAX2 and is not proteasome mediated,suggesting an alternative regulatory pathway.The ligand-induced degradation of receptors would effectively limit the duration and intensity of SL and KAR signaling.Phylogenetic analyses demonstrate that while KAI2 shows ubiquitous distribution across streptophyte lineages,whereas members of the D14 family are distributed only in seed plants,suggesting that D14 is evolved from KAI2 by gene duplications and neo-functionalization.These findings provide crucial insights into the origins of SL signaling pathways and establish a theoretical foundation for discovering endogenous KAR-like signaling molecules in plants.This review systematically summarizes the structural similarities and differences between SLs and KARs,along with recent research advances in their signal transduction mechanisms.Special emphases are placed on the identification of core signaling components of SLs and KARs,the molecular basis for specific recognition of structurally similar compounds,and the evolutionary relationships of key proteins involved in these pathways.We further highlight emerging research directions,including the search for endogenous KAR-like signals and novel components in SL and KAR signaling pathways.Deciphering these pathways will not only advance our understanding of plant signaling mechanisms but also offer novel strategies for crop architecture improvement and stress resistance breeding.