Origin, Evolution, Functional Diversitification, And Expression Correlation Of The RLK Gene Family Revealed In Jilin Ginseng, Panax Ginseng C.A.Mayer

The receptor-like protein kinase(RLK)-encoding gene family is one of the important gene families in plants; as a signal molecule receptor, it plays important roles in numerous biological processes, including plant biotic and abiotic stress tolerances and plant growth and development. This study has isolated the RLK gene family from our newly developed comprehensive unigene set of genes expressed in Jilin ginseng, characterized it at both the nucleotide and amino acid levels, investigated its origin and evolution, and decipher, for the first time, the functional diversification and expression of plant gene families using the Jilin ginseng RLK gene family as a model system. It is revealed that the Jilin ginseng RLK gene family is a super-gene family, consisting of at least 968 RLK genes. It originated before split between monocot and dicot plants. This gene family is shown to consist of eight subfamilies, but the LRR subfamily is the fundamental and oldest one, from which the remaining subfamilies were derived. It is also shown that although all members of the RLK gene family encode receptor-like protein kinases, they have been functionally diversified dramatically, participating in numerous biological processes. This result is consistent with the previous findings that the RLK gene family has multiple biological roles. The expressions of different RLK genes are extremely different in different plant tissues, at different developmental stages or in different genotypes, but the overall expression levels of the RLK genes involved in the same function are relatively consistent cross tissues, developmental stages or genotypes so that the cell’s demand for the gene’s products is met. The expressions of a vast majority of RLK genes are correlated, forming a co-expression network. Therefore, the findings and the ginseng RLK genes isolated in this study have significantly advanced our understanding of the functions and biology of gene families in plants and provided genomic resources and tools for enhanced breeding for disease resistance and environmental stress tolerance, and regulation of plant growth and development in ginseng.