The Effects Of Specific Expression Of Auxin Synthesis Gene IaaM In Transgenics’ Phloem

Auxin is the first plant hormone discovered in experimental biology, it is virtually involved in every aspect of plant growth, development and morphogenesis. It also plays an important role in vascular differentiation and vascular formation.Auxin (mainly is3-indoleacetic acid, IAA) can be synthetized through at least four pathways that are not illustrated completely. The iaaM. gene found in bacteria Agrobacterium tumefaciens or pseudomona coding an enzyme of tryptophan monooxygenase (IaaM) which can catalyze tryptophan into Indole-3-ethylamine and that further be transformed into IAA by chemical hydrolysis or non-specific aminohydrolyse in plant. The iaaM gene expression can lead some seriously phenotype of the plant.We constructed a plant phloem specific expression iaaM vector by recombined the iaaM with the phloem-specific promoter, sucrose synthesis gene promoter of Arabidopsis thaliana. The recombinant is transformed into Nicotiana tabacum and Arabidopsis thaliana successively to study the effects on vascular differentiation and organ development after over synthesis of IAA in transgenics’phloem.The specific expression iaaM gene was transformed into Arabidopsis thaliana and Nicotiana tabacum via Agrobacterium tumefaciens inflorescence filtration and leaf-disc co-culture transformation respectively. Several transgenics are screened out through hygromycin selection and molecular detection. Most of the transgenetic plants showed abnormal morphologies both with Nicotiana and the Arabidopsis such as leave curling, slower growth with smaller plantlet. In addition, some of the transgenetic stems produced many adventitious roots as air roots and numerous root hairs and lateral roots occurred. The tissue dissection showed the stem developed some more secondary xylem and phloem cells than wild-type control.The results show the expressing IAA specifically in transgenics’phloem will influence of the plant development as comprehensive and integrity. It is reasonable that the phloem is an important channel for auxin long distance transport. The accumulated auxin which is excessive expressed in phloem can be redistributed in a distance or polar transport make the auxin distribuation remodel and leading the plant produce a series of changes in the local or whole morphology. We can explore the auxin function through these changes more deeply and precisely.