Expression And Function Of Inositol Oxygenase Gene In Malus Hupehensis Rehd

Soil salinization are the global problems that restrict agricultural and forestry production.Abiotic stresses such as drought,high salt and saline impact on the plant growth and metabolism.After long-term development,plants can resist these abiotic stresses through various mechanisms such as osmotic adjustment and antioxidant regulation.It has been found that myo-inositol?MI?plays an important role in plant stress resistance.Inositol-1-phosphate synthase?MIPS?is the rate-limiting enzyme during inositol biosynthesis.Whil,inositol oxygenase?MIOX?is a key enzyme of catalyzing catabolism.At present,most of the studies about MIOXare maily focused on herbaceous plant such as Arabidopsis thaliana,but there are few reports of MIOX on woody plants.Excavating the MIOX gene of apple rootstock and its functional research not only has important theoretical significance,but also has wide application value,which can provide potential effective candidate genes for plant anti-retroviral research,In this study,a MIOX gene named MhMIOX1 was cloned from Malus hupehensis Rehd,and its encoded amino acid sequence was compared,and its expression pattern and its function were analyzed.The main research work and results are as follows:1?A gene sequence encoding MIOX was isolated from Malus hupehensis Rehd and named MhMIOX1.MhMIOX1 encodes 333 amino acids,and the amino acid sequence encoded by MIOX gene of Malus hupehensis Rehd has the highest amino acid sequence homology with the MIOX gene of other species and the highest peach in woody plants,with a similarity of more than 90%.2?We treated the tissue culture seedlings of Malus hupehensis Rehd with NaCl,PEG and AB respectively.The response of MhMIOX1 to these three abiotic stresses was analyzed by RT-PC.The results showed that all the three stress treatments caused the up-regulation of MhMIOX1 expression.It is speculated that MhMIOX1 may play an important role in plant response to abiotic stress.3?In order to verify the role of MhMIOX1 gene in the response to salt stress,we first used the herbaceous model plant Arabidopsis thaliana to analyze its function.The results showed that overexpression of MhMIOX1 increased the germination rate,root length and growth of Arabidopsis thaliana under salt stress treatment.The MhMIOX1gene was further transformed into the woody model plant Shanxin Yang.Under salt stress treatment,the growth of MhMIOX1 plants was significantly better than that of wild type.The above results indicate that overexpression of MhMIOX1 can increase the tolerance of plants to salt stress.4?We further studied the effect of MhMIOX1 overexpression on the accumulation of reactive oxygen species in transgenic poplars.The results showed that the contents of H₂O₂ and MDA in wild type and transgenic MhMIOX1 were increased with salt concentration under different salt stresses,but at the same NaCl level,the accumulation of H₂O₂ and MDA in MhMIOX1 was increased.It is significantly lower than the wild type,and the activities index of antioxidant enzymes such as peroxidase?POD?,ascorbate peroxidase?APX?and catalase?CAT?are significantly higher than those of the wild type strain.This indicates that the overexpressed MhMIOX1 gene can enhance the activity of antioxidant enzymes,reduce the content of reactive oxygen species,reduce the damage of reactive oxygen species to the cell membrane,and thus improve the resistance of plants.