| As the fast growth woody grass plant,Moso bamboo(Phyllostachys edulis)can supply edible shoots,building materials,furniture raw materials and so on within a relative short time.The young Moso bamboo winter shoots covered with a shell emerge from the ground to grow into spring shoots,then rapid growth occurs.However,the molecular reactions of bioenergetic processes which are essential to fast growth remain undefined,and the molecular mechanism of palatability difference between winter and spring shoots caused by carbohydrate metabolism during this process are still unclear.Herein,the mitochondria were successfully isolated from winter and spring shoots of Moso bamboo,and a combined analysis using physiology,cytology,transcriptome and proteome approaches were performed to reveal energy regulation mechanism of rapid growth initiation in Moso bamboo.Besides,the research further studied the abiotic stress resistance function of PeAOX1b＿2,a member of alternative oxidase(AOX)gene family related to energy metabolism in Moso bamboo.Moreover,the molecular regulation mechanism of palatability difference between winter and spring shoots was elucidated through integrated transcriptome and metabonomics analyses.The main results are as follows:(1)Numerous key genes and proteins responsible for energy metabolism were significantly up-regulated in spring shoot including those involved in starch and sucrose catabolism,glycolysis,pentose phosphate pathway,tricarboxylic acid cycle and oxidative phosphorylation.Accordingly,significant decrease of starch and soluble sugar,higher ATP content,higher respiration rate and glycolysis rate were identified in spring shoot.Besides,the up-regulated genes and proteins related to mitochondrial fission and significantly increased mitochondrial numbers indirectly promoted the process of intracellular energy metabolism.Moreover,enhanced alternative oxidase and uncoupled protein pathway in winter shoot reflected that an efficient energy-dissipating system was important for winter shoot to adapt to low-temperature environment.(2)Under salinity,drought and low-temperature stresses,the ectopic overexpression of PeAOX1b＿2 in Arabidopsis enhanced seed germination and seedling establishment,increased the respiratory intensity and the proportion of AOX respiratory pathway in leaf,and enhanced osmotic tolerance and antioxidant ability,suggesting that PeAOX1b＿2 may be crucial for abiotic stress resistance in Moso bamboo.(3)The significant increase of gallic acid promoted the content of hydrolyzed tannin,leading to the increased bitterness of spring shoots.This process was positively regulated by key enzyme genes involved in the hydrolyzed tannin synthesis pathway.In addition,cinnamic acid,ferulic acid,UDP-glucose and UDP-xylose were identified as the differentially accumulated metabolites related to roughness of Moso bamboo shoots,and their significant accumulation increased the contents of roughness materials(lignin,cellulose and hemicellulose).Accordingly,this process was positively regulated by most enzyme genes involved in lignin,cellulose and hemicellulose synthesis pathway.Overall,this thesis highlights the power of comparing total and mitochondrial omics and integrating physiochemical data to understand how bamboo start fast growth by modulating bioenergetic processes and how metabolism of energy substances lead to palatability difference in bamboo shoots.On the one hand,this study provides a high-resolution map of the molecular network for energy production and dissipation in Moso bamboo shoot and enriches our understanding of the molecular mechanisms underlying plant fast growth.On the other hand,this study reveals a metabolic molecular regulatory network for differences in bitterness and roughness between winter and spring bamboo shoots caused by consumption of non-structural carbohydrates and accumulation of structural carbohydrates.The data sets provided here will ultimately inspire biotechnological strategies for plant growth improvement in woody plants and crops. |
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