Response Of AlaAT Transgenic Poplar To Nitrogen

Populus simonii × Populus nigra has many excellent traits such as drought resistance and cold tolerance,and is a tree species promoted by afforestation in the north.Nitrogen is an essential nutrient element in plant growth and development.Alanine aminotransferase is a key enzyme in nitrogen assimilation.The enzyme is widely distributed in various plant tissues and organs,and its enzyme activity is not only found in leaves.It is also found in roots and flowers,and in other tissues such as endosperm tissues of fruits and rice seeds.The extensive distribution of AlaAT also demonstrates its important role in the metabolism of plants throughout their life cycle.In this experiment,the AlaAT gene was used as a test material to investigate the role of AlaAT in nitrogen metabolism of poplar by measuring the growth index and physiological index of P.simonii ×P.nigra.The main results are as follows:(1)In order to investigate whether the transgenic AlaAT gene is different from wild-type.simonii ×P.nigra in the phenotype,two growth indexes of plant height and ground diameter of 17 transgenic lines and wild-type plants were detected after two months of growth.As well as photosynthesis indicators,the plant height and ground diameter increase of most transgenic lines were found to be better than that of wild type plants.Among them,the plant height increments of the 3rd and 7th transgenic plants were the largest,and the ground diameter increments of the 2nd and 6th transgenic plants were wild type.Plants showed extremely significant differences,and all transgenic lines had higher ground diameter increments than wild-type plants.In the detection of photosynthesis index,the net photosynthetic rate of transgenic plants was higher than that of wild-type plants,and the net photosynthetic rate,stomatal conductance and transpiration rate of other transgenic lines were lower than those of wild-type plants.(2)By detecting the activity of alanine aminotransferase in the transgenic AlaAT gene.simonii ×P.nigra,we found that the alanine aminotransferase activity in the leaves of most transgenic lines was significantly higher than that in the wild type plants,the transgenic plants of No.8 and the transgenic plants of No.17 The enzyme activity is the highest.In the roots,only 5 transgenic lines were significantly different from wild-type plants,and the 2 and 13 transgenic plants had the highest enzyme activity in the roots.We screened two No.2 and No.13 in the roots and leaves which were significantly higher than the wild type plants,and two plants 15 and 16 in the leaves which were significantly higher than the wild type plants but with similar enzyme activities in the roots.A total of 4 transgenic lines were used to carry out subsequent studies on the response of AlaAT gene to P.simonii × P.nigra.(3)When wild-type plants and 4 transgenic AlaAT plants were treated with 1 mmol/L NaNO3,the activity of GS enzyme activity in roots was low.Within a certain range,with the increase of NaNO3 concentration,the GS enzyme activities in the roots of transgenic lines would be different.Increase.In the leaves,the activity of GS in the lower leaves was higher than that in the upper leaves.When the concentration of NaNO3 increased,the activity of GS in the leaves of 13 and 16 transgenic plants increased significantly.When treated with 1 mmol/L NH4Cl,the GS activity of roots of transgenic lines was significantly higher than that of wild type plants.With the increase of concentration,the GS activity of roots of transgenic lines decreased slightly,which was similar to that of wild type plants.2 mmol/L NH4Cl had no effect on the GS enzyme activity in the upper lobe.In the treatment of NaNO3,the GOGAT activity in the leaves of each plant increased with the increase of NaNO3 concentration,and the 13th transgenic plants were the most significant.When the concentration of NH4Cl increased,the activity of GOGAT in the upper leaves was stable,and the activity of GOGAT in the lower leaves of the transgenic plants decreased.(4)We treated wild-type plants and transgenic lines with 2 mmol/L NaNO3,2 mmol/L NH4Cl,1 mmol/L NaNO3 and 1 mmol/L NH4Cl,and detected 10 genes related to nitrogen metabolism.The expression levels in different tissues after treatment were as follows:When the concentration of nitrate nitrogen increased from 1 mmol/L to 2 mmol/L,the expression of AlaAT1 in roots and leaves of transgenic plants was promoted,the expression of AlaAT3 in leaves,the expression of AlaAT4 in lower leaves and roots,and roots were promoted.Expression of AspAT gene in the upper lobe,expression of NR in the lower lobe,expression of NADH-GOGAT in the upper lobe,expression of NIR in the lower lobe,expression of NRT1.1 in the root,and ammonium nitrogen promoted AlaAT4 in the upper lobe Expression,expression of AspAT in roots,and expression of NR and NADH-GOGAT in the lower lobe and expression of NRT 1.1 in the upper lobe.It can be seen that nitrate nitrogen is the main nitrogen source affecting transgenic plants,and both nitrogen sources regulate the nitrogen metabolism-related genes of transgenic plants to varying degrees.Among them,the transgenic plants of No.2 and the transgenic plants of No.13 were significantly affected by different nitrogen treatments.