The Origin And Evolution Of A Theanine-Associated Regulatory Module In Non-Camellia And Camellia Species

Theanine(thea)is one of the most important plant-derived characteristic secondary metabolites and a major material of health care products due to its beneficial biological activities,such as anti-anxiety,promoting memory and lowing blood pressure.Thea mostly accumulates in Camellia plants and is especially rich in Camellia sinensis(tea plant).Although some function genes(e.g.TS,GOGAT,GS)attributed to thea accumulation have been separately well-explored in tea plant,how these genes related to thea metabolisn interact with other unknown functional genes such as transporter genes and TFs to form thea-associated regulatory module(TARM)and the evolution of regulatory module(highly-interacting gene group)related to thea metabolism remains to be elaborated.To explore above questions,we constructed a global gene coexpression network and successfully mined TARM based on mRNA sequencing data of tea plant.Subsequently we explored the evolutionary trajectory of TARM between Camellia species and non-Camellia species.Furthermore,we screened two high-credible transcription factors(TFs)regulating TS1.The main conclusions are as follows:1.TARM was mined by using a comprehensive analysis of weighted gene co-expression network based on mRNA sequencing data from different tissues of tea plant.TARM highly correlated with the root tissue of tea plant and genes are highly expressed in tea root.More importantly,TARM almost contain all of the basic biosynthetic genes related to the thea metabolic pathway and other important genes encoding thea transporters.2.Comparative genomic analysis of 84 green plant species revealed that TARM originated from the ancestor of green plants(algae)and that TARM genes were recruited from different evolutionary nodes with the most gene duplication events at the early stage.3.Among the TARM genes two core TFs named NAC080 and LBD38 were deduced,which may play a crucial role in regulating the biosynthesis of thea.Our findings provide the first insights into the origin and evolution of TARM and indicate a promising paradigm for identifying vital regulatory genes involved in thea metabolism.Meanwhile,our study also provides a paradigm to mine genes underlying the characteristic pathways of plants based on the cross-species network evolutionary model.