| Cassava is the euphorbiaceae cassava dicotyledonous plants, which originated in South America amazon river basin. Cassava root can accumulate a large amount of starch, which is used as an important promoting cultivation of food crops. Cassava is a typical C3plant, but has the characteristics of C4plants photosynthesis. However, cassava starch accumulated in the roots is much lower than the theoretical value. It is reported that the amount of photosynthate produced by leaves transfers to the roots for strach accumulation is less than1/5. So it is meaningful to improve the energy transferring rate from leaves to roots. Sucrose is the main form of light compound transportation, and invertases irreversibly hydrolyze sucrose into glucose and fructose. It plays important role in the progress of the phloem loading-transportation unloading to library organization. Sucrose cell wall invertase, the key enzyme of the sucrose-metabolizing enzymes, transfers photosynthate from leaves to roots and inevitably involved in plant growth and development, signal transduction, biological and abiotic stress response, such as a variety of physiological processes.In this study, based on the known coding domain sequences of cassava cell wall invertase genes and the phytozome plant gene sequences prediction library, we designed primers and PCR amplified. Then a130bp coding domain sequence of the MeCWINV2gene with906bp promoter region, a130bp coding domain sequence of the MeCWINV5gene with1170bp promoter region, and a118bp coding domain sequence of the MeCWINV6gene with1042bp promoter region were isolated and submitted to GenBank as the accession numbers of MeCWINV2(KC465191), MeCWINV5(KC465193) and MeCWINV6(KC465192).PlantCARE bio-informatics’analysis showed that the MeCWINV2, MeCWINV5, MeCWINV6gene promoters contain several CAAT boxes and TATA boxes, which are the typical eukaryotic promoter elements. They also contain a lot of elements, such as light, hormonal and stress-related components, which the GARE-motif elements of response by GA, which the TC-rich elements of defense and so on. Each gene promoter elements exist on differences. Speculation MeCWINV2, MeCWINV5and MeCWINV6structure characteristics of the three gene promoter and according to the combination of introns-explicit substructure and analysis of the three genes in genome structure information have homology and differences on the gene expression.According to bio-informatic analysis that some cis-acting elements which relate to hormonal and stresses are found in the promoters of MeCWINV2, MeCWINV5and MeCWINV6, thus,the low temperature stress16℃,4℃,20%PEG6000drought stress, and four kinds of exogenous hormones as30u M GA3,100μ M SA,30μ M ABA and1%ethephon were used to treat the plantlets of SC8, then detected the gene expression levels of MeCWINV2, MeCWINV5, MeCWINV6. using RT-PCR technique. The results showed that the MeCWINV2gene was not expressed under any the normal environment and various stress conditions; MeCWINV5gene increased its expression as the treated temperature decrease and treatment time addition; and also the GA3and ABA treatment could affect its expression, but SA and ethephon treatment had no significant effect on its expression. The activity of MeCWINV6was not detected under normal culture conditions, PEG6000drought and ethephon treated conditions; whereas,the low temperature, ABA and SA treatment were significantly increased its expression. It deduces that the gene expression of the cell wall invertase in cassava under stresses may correspond to the cis-acting elements in their gene promoters. |
