| Epidermal wax is a hydrophobic structure located in the outermost layer of plants.It is mainly composed of lipid compounds such as alkanes,alcohols,ketones,aldehydes,esters,fatty acids and other substances.Wax can be used as a natural protective layer to reflect excess UV rays before harvest and prevent sunburn.And can prevent excessive evaporation of water,play the role of water retention;It can also reduce the wettability of plant surface and reduce the attachment of pathogenic bacteria.Therefore,the increase of wax accumulation in apple pericarp can also improve the quality of postharvest storage,prolong the shelf life and improve the value of apple.During plant epidermal wax synthesis,C16:0 and C18:0 short-chain fatty acids form precursors for wax synthesis under the action of Long-chain Acyl-Co A synthetases(LACSs).VLCFAs are then generated by fatty acid elongases,and VLCFAs undergo the alcohol synthesis pathway and alkane synthesis pathway to generate VLCFAs derivatives such as fatty aldehydes,alkanes,fatty alcohols,ketones,and esters,etc.Thus,the LACSs genes have a very important role in the wax synthesis process of plants.Although the LACSs genes have been extensively studied in Arabidopsis thaliana,its evolutionary mechanism and function in apple,however,are still not clear enough.In this study,the functional characterization of apple Long-chain Acyl-Co A synthetase 1(LACS1)revealed its ability to promote wax synthesis and to resist abiotic and biotic stresses.The relevant findings are as follows:1.Md LACS1 promotes epidermal wax accumulation.The expression levels of Md LACS1 in different tissues of apple root,stem,leaf,flower,pericarp and sarcocarp were detected,and the highest expression level of Md LACS1 was found in pericarp.Md LACS1 was expressed in apple pericarp by transient gene expression,and it was found that Md LACS1 promoted waxy accumulation in apple peel by scanning electron microscopy.In order to further verify the function of Md LACS1 in promoting waxy synthesis,heterologous expression of Md LACS1 was obtained in Arabidopsis thaliana.Waxy extract,analysis of waxy composition by GC-MS and scanning electron microscopy showed that Md LACS1 promoted the accumulation of waxy epidermis.The chlorophyll leaching and leaf water loss experiments of Arabidopsis thaliana with heterologous expression of Md LACS1 showed that the epidermal permeability of stems and leaves of Arabidopsis thaliana with heterologous expression of Md LACS1 decreased.2.Md LACS1 enhanced drought resistance of plants.The wild-type calli,Md LACS1 transgenic calli and anti Md LACS1 calli were treated with 6% PEG6000,and it was found that Md LACS1 improved the osmotic stress resistance of calli.The drought resistance of wild Arabidopsis thaliana and Md LACS1 heterologous expression Arabidopsis thaliana was significantly enhanced under drought treatment.3.Md LACS1 enhanced salt tolerance of plants.The wild-type calli,Md LACS1 transgenic calli and anti Md LACS1 transgenic calli were treated with 150 m M Na Cl.Md LACS1 improved the salt-resistance of the calli.The 150 m M Na Cl treatment of wild-type Arabidopsis thaliana and Md LACS1 heterologous expression of Arabidopsis thaliana further demonstrated that transgenic plants improved their resistance to salt stress.4.Md LACS1 enhances plant disease resistance.When B.dothidea was inoculated against wild-type calli,Md LACS1 transgenic calli,and anti Md LACS1 transgenic calli,mycelia spread the slowest on the surface of Md LACS1 transgenic calli,while faster on the surface of anti Md LACS1 transgenic calli.q RT-PCR results showed that Md LACS1 increased the expression level of resistance genes in calli.Md LACS1 was injected into Arabidopsis thaliana and wild-type Arabidopsis thaliana with Pst DC3000 bacteria,and it was found that the leaf yellowing degree of transgenic plants was lower than that of wild-type Arabidopsis thaliana.Md LACS1 enhanced plant disease resistance by changing the expression level of endogenous immune genes and promoting wax synthesis. |
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