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                        <td width="82%">&nbsp;</td>
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                        <td valign="top"><img src="images/borthakur_d.jpg" width="100" height="140"></td>
                        <td width="579" valign="top" ><p align="left"><span class="head1">Dr. 
                            Dulal Borthakur </span><br>
                            Professor<br>
                            <br>
                            Professor of Molecular Biology and Biotechnology <br>
                            Department of Molecular Biosciences and Bioengineering 
                            (MBBE) <br>
                            University of Hawaii-Manoa <br>
                            1955 East-West Road, Ag. Science 218<br>
                            Honolulu, Hawaii 96822, USA <br>
                            <br>
                            Office: Agriculture Sciences Bldg. 415F <br>
                            Telephone: (808) 956-6600<br>
                            FAX: (808) 956-3542 <br>
                            Email: <a href="mailto:dulal@hawaii.edu ">dulal@hawaii.edu 
                            </a></p>
                          <p align="left"><strong>Courses Taught:</strong><br>
                            BIOL 401 (Spring)</p>
                          <p><strong>Plant-microbe interactions</strong><br>
                            <br>
                            The research program in my laboratory concerns the 
                            regulation of genes in the rhizosphere bacteria by 
                            compounds present in the root exudates of plants. 
                            The rhizosphere of plants is a highly complex and 
                            dynamic ecosystem due to the continuous supply of 
                            organic material from the plants as root exudates. 
                            Many of the compounds in the root exudates can serve 
                            as chemoattractants for rhizosphere bacteria at micromolar 
                            concentrations. We are using the tree legume Leucaena 
                            leucocephala and its nitrogen-fixing micro-symbiont 
                            Rhizobium as a model system to study the role of certain 
                            compounds in the plant root exudates on plant-microbe 
                            interactions. Leucaena plants contain a free amino 
                            acid, mimosine, which is toxic to animals and microorganisms. 
                            Mimosine has general antimitotic activity that blocks 
                            the cell cycle in the late G1 phase. One of the degradation 
                            products of mimosine, 3-hydroxy-4-pyridone (HP), causes 
                            goiter, loss of hair and reduced productivity when 
                            fed to animals. We found that mimosine is present 
                            in the root exudates of Leucaena. We have also shown 
                            that some Rhizobium strains isolated from the nodules 
                            of Leucaena trees degrade mimosine (Mid+) and are 
                            able to utilize it as a source of carbon and nitrogen. 
                            The enzymes for mimosine degradation in the Mid+ strains 
                            are induced by mimosine. Recently, we have cloned 
                            and sequenced five mid genes involved in degradation 
                            of mimosine into HP from the Mid+ Rhizobium strain 
                            TAL1145. We have also cloned a DNA fragment containing 
                            pyd genes for degradation of HP into pyruvate, formate 
                            and ammonia. Our goal is to determine the role of 
                            mimosine in bacterial-plant interactions by studying 
                            the population dynamics of mimosine-degrading bacteria 
                            in the Leucaena rhizosphere. We are in the process 
                            of characterizing mid and pyd genes and determining 
                            how the expressions of these genes are regulated in 
                            the rhizosphere and the Leucaena root nodules. </p>

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