Study On The Characteristics Expression Of CsLOXs Gene In Cucumber Fruit

Lipoxygenase(Lipoxygenase, LOX), also known as fatty oxidase, carotene oxidase,oxygenase or oxygenase, is a protein containing the heme iron. It was reported that there’re a total of 12 lipoxygenase expressed during cucumber fruit development. But the regulatory mechanism between LOX gene and the formation process of C6, C9 aldehyde aroma substances is not clear. This test focused on the 26 and 14 cucumber germplasm which has different aroma composition, cattied on the cloning, bioinformatics analysis and expression patterns of cucumber CsLOXs genes family, analysis of the corresponding enzyme activity and so on. We preliminarily discussed the function of lipoxygenase(LOX) gene, lay the foundation of cucumber aldehyde aroma substances fomation molecular mechanism. The main conclusions of this test are as follows:1. Cloning and bioinformatics analysis of the family of CsLOXs. We cloned and carried on the bioinformatics analysis of the eight CsLOXs which expressed in cucumber fruit. It was showed that they all contain the characteristics of the plant LOXs domain structure, of which two belong to 9-LOXs(CsLOX9, CsLOX10), six belonged to 13-LOXs(CsLOX16, CsLOX19,CsLOX17, CsLOX22, CsLOX8, CsLOX2), and four belong to the type TypeI(CsLOX8,CsLOX2, CsLOX9, CsLOX10), four belong to the type TypeII(CsLOX16, CsLOX19,CsLOX17, CsLOX22). CsLOX9 and 9-LOX(accession No. AJ271161)sequence homology was 99.8%, CsLOX16, CsLOX19, and CsLOX17 homology between 60% or more.2.The expression pattern analysis of CsLOXs gene during cucumber fruit development period. Research showed that the expression of different CsLOXs gene in cucumber fruit development process and its epicarp, mesocarp, endocarp has significant differences. In 26 species, as the fruit development process CsLOXs gene expression has reduce(high- low),reduce after increase(low- high- low), increase after reduce(high- low- high), and gradually increase(high- low) four models; The gene expression in 14 species act the same.Most gene expression model in the three layers of skin is epicarp > mesocarp > endocarp. In the process of cucumber fruit development, 26 germplasm reduce after raise, reached maximum at 12 d, and 14 species LOX enzyme activity falling. PCA analysis shows that 13-LOXs, C6 aldehydes and LOX activity belong one group, and 9- LOXs and C9 aldehyde belong to the other group.3. The CsLOXs family gene expression analysis of cucumber fruit under different storage temperatures. Studies showed that under the condition of 25℃, no obvious change in the gene expression. When 4℃, the expression of CsLOX19, CsLOX9 has no obvious change with the extension of storage time, while CsLOX22, CsLOX23, CsLOX20, CsLOX22, CsLOX16,CsLOX2, CsLOX10 expression is increase before decline. CsLOX19, CsLOX9, CsLOX22,CsLOX23 have response to the storage temperature 25℃, while CsLOX20, CsLOX22,CsLOX16, CsLOX2, CsLOX10, CsLOX19 are response to 4℃ storage temperature.4. Study of the MeJA, damage and SA treatment effect on CsLOXs family gene expression patterns. For 14 germplasmfruit, after exogenous MeJA and damage processing,the CsLOX9 expression declines, and the rest of the LOXs gene expression is increase before decline. Total LOX enzyme activity is increased before reduced. For the 26 seedling, LOXs genes expression has no obvious change, reducing, increase after decrease and increase before reduction four expression patterns. CsLOX22 and CsLOX8 are not sensitive to MeJA processing, and CsLOX20 is not sensitive to the SA treatment. In SA and JA signaling pathways, CsLOX19, CsLOX2, CsLOX9 and CsLOX10 have antagonism while CsLOX23 has synergy.