Molecular Evolution Of The WRKY Gene Family Of Land Plants

The WRKY gene family is widely involved in many important physiological processes of plants,especially the defense responses of abiotic stress and biotic stress.Therefore,it is of great significance to study the evolution of WRKY genes in early land plants.This paper collected a large number of algae,lichens,ferns,gymnosperms and angiosperms genomes and transcriptome data,preliminary analysis obtained the evolutionary path of WRKY gene from green algae to higher land plants.Compared with the seven subfamily classifications widely used before,the WRKY gene of green plants is more suitable to be divided into five subfamilies(Group I,IIa + IIb,IIc,IId + IIe,III).The WRKY gene was not detected in Rhodophyta and Glaucophyta,both group I and group III contained green algae sequences,indicating that they originated at least from green algae.The number of WRKY genes in terrestrial plants increased sharply,and the distribution of species in subfamily I and IIc was similar,but the number of early land plant sequences in Group IIc was significantly higher than that in Group I,indicating that specific expansion occurred in Group IIc.Except for only one branch of gymnosperm in subfamily III,there are 1.5 branches of early land plants in all five subfamilies,while the seed plants have an average of 3 branches.The WRKY gene exhibits significant and specific amplification in the terrestrial plant genome and,in addition,has specific expansion in different species.Moss has many members in Group IIa,IIc and III,but the difference between Physcomitrella patens and Sphagnum fallax in different subfamilies is up to 50%.The ferns are mainly distributed in Group I and IIc and have no members in Group III.A highly amplified coniferous monophyletic group was present in subfamily IIa + IIb and IIc,while no similar phenomenon was observed in other subfamilies.The Nymphaea colorata and the Amborella trichopod,which belong to the original angiosperm,differ greatly.The number of WRKY genes in N.colorata is almost twice that of A.trichopod.In combination with the function of the existing WRKY gene,according to the similar function of the homologous gene,it is speculated that the above amplification event may be related to the resistance of the plant to the land environmental unfavorable factors such as drought and high temperature.Based on the above results,we propose the evolutionary hypothesis of the WRKY gene in terrestrial plants: the WRKY gene first appeared in the green algae genome,and experienced two large-scale amplification events in terrestrial plants for the first time in the initial landing of the moss period.The mark is an increase in the WRKY subfamily type,which is increased from only the subfamily I III adverbial clauses to the current five major families;the second occurs during the evolution of ferns to seed plants,marking the explosive growth of the number of WRKY genes.In addition to these two expansions,there is a clear expansion in different species.These results increase our understanding of the origin and evolution of WRKY transcription factors in terrestrial plants,which in turn suggests that the WRKY gene plays an important role in the early origin of terrestrial plants.