Identification Of Genes Involved In Wood Formation Using Arabidopsis Thaliana Mutants

Wood formation is a comprehensive process which possesses thousands of genes underprecise control. To understand the molecular mechanism of wood formation, a quick andefficient method is necessary to study the function of these genes. Arabidopsis can produceconsiderable amounts of secondary xylem under certain condition, which can mimic theprocess of wood formation. In this study, the induced Arabidopsis secondary growth system areapplied to verify the function of genes previously obtained may involved in the development ofsecond vascular system in poplar.According to information of differentially expressed genes during regeneration ofsecondary vascular system in poplar, we obtained 151 Arabidopsis mutant lines comprising 89Arabidopsis genes form mutants center of NASC, RIKEN, CSHL. These were raised underinducing condition to test if any morphology and structure changes. Twenty two Arabidopsismutants had various changes in morphology and anatomical structures. Twenty mutants hadlow germination rate from 10% to 60%, of which 2 had survival rates at 0% and 50%. Fivemutants occurred structure changes in the hypocotyls or stem. One of these lines, namedarris-stem (as), showed some unique changes: slower growth rate in comparison with the wildtype from germination to florescence; serrated margin of leaf blades, spiral rosette; morebranch in the bottom part of the stem, shorter nodes, twisted stem and branch. There were oneor several arrises along the stem. Across sections of the arrises showed one or several compactcells lumps which were round, made up of several layers of cells, looked like vascular-bundle.The tissue was more fluorescent under UV light than the surrounding cells, which suggestedthere was the thickened cell wall. Tracheary elements were observed inside the arrises undermicroscope, suggesting they are similar to vascular bundles.According to information from Arabidopsis Mutants Center(http://signal.salk.edu/),T-DNA insert site located in the gene At2g44110. The At2g44110 gene functions wereinvestigated with three approaches, i. e., gene complementary; gene express profile; geneover-expression. The results showed that the phenotype of as mutants came to the normal aftergene complement. The expression profiles showed that the as gene was mainly expressed inthe vascular bundles of the inflorescence, young leaves, and also presented in bundle in young root and stem. The express occurred only in young tissues, and no express was found in oldleave and stem. The transformants intended to over-expression of the gene was obtained butnot characterized yet.Based on the complementary study on the as mutants, we suggest T-DNA insertion of theAt2g44110 cause the as phenotype. In addition, its expression pattern indicated that this geneexpressed in the primary growth stage of the stem. These results indicate it may predetermineon the potential vascular development pattern and also fimction in the later development of thevascular systems.This study showed that as may play an important role in the vascular system developmentin the Arabidopsis, and this gene have been found differentially expressed in the secondaryvascular system in poplar (Populus tomentosa.). Taking together we suggest that Arabidopsisand poplar may be similar in the vascular system development and regulation mechanisms.This study may serves as an example to study functions of genes involved in wood formation,using the induced secondary vascular system in Arabidopsis, which could provide the basicdata to elucidate the molecular mechanisms of the development of the secondary vascularsystem.