Study On The Synthesis And Regulation Of Cuticular Wax At High Carbon Dioxide Concentration

Accumulation of carbon dioxide leads to a series of biological and ecological problems,which strongly influencing the normal development of plant species and causing Greenhouse Effect via indirect increasing global temperature.Wax layer,covering the aerial tissue and organ surface of terrestrial plants,works as first barrier against environmental stresses.Cuticular waxes are comprised of very-long-chain fatty acids(VLCFAs)as well as other derivatives,such as aldehydes,alkanes,primary alcohols,secondary alcohols,ketones and wax esters.As a kind of hydrophobic materials,cuticular waxes play important role in various biological processes and are able to help plant regulate non-stomatal water loss and gas exchange,avoid biotic and abiotic stresses damages,such as ultraviolet(UV)light or high irradiation and affection of fungi or insects.Although mechanisms of cuticular wax biosynthesis,transport,and regulation have been studied in Arabidopsis thaliana in the past few years,genes regarding to carbon dioxide sensor and wax synthesis of leaf epidermis-specific are poorly reported.Here,we discussed these two issues,respectively.Here are the results:1)After plant treated with elevated carbon dioxide concentration,the total amounts of cuticular wax were reduced,and the alkanes reduced by 54.7%;qRT-PCR confirmed this result,the expression level of CER1,the key gene involved in alkanes biosynthesis,reduced 3.5 folds.Moreover,transcriptome analyses revealed that expression level of CER1,CER3 and KCS1 have dropped with different degree.Expression of positive transcriptional regulator,such as MYB96 and MYB94,are reduced,on the contrary,negative transcriptional regulator HDG1 significantly increased.Above results indicated that high concentrations of carbon dioxide might inhibit the synthesis of alkanes,which would in turn decrease the amount of cuticular wax.2)By comparing the transcriptome data from epidermis and leaves,we found that not all the wax biosynthesis genes were induced in epidermal cells as we expected.Although the expression of LACS1,CER6 and CER2 that involve in fatty acid elongation have increased,the alkanes and primary alcohol synthase related genes,such as CER1 and CER4 reduced 87%and 95%respectively.In addition,other differential expressed genes,including ABCG11 and LTPG1,LTPG2,HDG1 are needed further study.3)The differential expressed SPL13 was selected for further study.Overexpression of SPL13 led to significant increase of cuticular wax.Specifically,alkanes and primary alcohol wax showed the most noticeable increase in mSPL13 leaf.The results indicated that SPL13 might be involving in both alkane-forming and alcohol-forming pathways.More researches are needed to figure out the role of SPL13 in regulating of cuticular wax synthesis.