62. 
Transgenic rice harboring legume ENOD4O gene
M. 
Dey1, L.B. Torrizo’, R.K. Chauduri3, P.M. Reddy2, J.K. Ladha2, K. Datta1 and S.K.
Datta1*
1) 
Plant Breeding, Genetics and Biochemistry Division, International Rice Research Institute, P.O. Box
3127, 1271 Makati City, Philippines
2) 
Soil and Water Science Division, International Rice Research Institute, P.O. Box 3127, 1271 Makati 
City, Philippines
3) 
Department of Botany, University of Calcutta, Calcutta-700019, India

 
     Nitrogen is critical for plant growth. There has been much interest in exploring the feasibility of transferring symbiotic nitrogen fixation capability to important cereals such as rice. Considering the need for a continuous supply of mtrogen for enhanced rice yield, taking a methodical stepwise approach, we are analyzing ability of rice to enter into nitrogen-fixing symbiosis with rhizobia akin to that in legumes.
     The early nodulin gene ENOD4O is one of the several host plant genes involved in the nodulation ability in legumes. ENOD4O has been proposed as playing a pivotal role in the induction of cortical cell division leading to the initiation of the formation of nodule primordium in legume roots in response to rhizobial interaction (Mylona et a!. 1995, Charon et a!. 1997). Expression of this gene in the plant parts other than in nodules, nevertheless, suggests its probable dual role in symbiotic as well as non-symbiotic organogenetic process (Papadopoulou eta!. 1996). Recent findings indicate the involvement of ENOD4O in differentiation and/or the function of stem vascular bundles (Kouchi et a!. 1999).
     In order to study whether ENOD4O is able to induce developmental changes similar to that in legumes we have transformed rice with MtENOD4O gene driven by CaM V35S promoter (Fig. 1). This is the first report of transgenic rice expressing an early nodulin gene from legume. Independent transformation events and integration of the transgene were confirmed by Southern blot analysis. Northern blot analysis and reverse transcriptasePCR were performed to confirm the transcription of the transgene. The shoot growth and phenotype of the first generation plants were altered to varied degrees. Presently we are investigating the probable involvement of this gene in vascular tissue differentiation in rice.
     Recently we have also obtained transgenic rice (Moul Dey et a!. in preparation) carrying soybean GS5O, a homologue of the putative Nod factor receptor gene DB46 from Dolichos biflorus (Etzler et a!. 1999). We intend to generate hybrids by crossing the stable transgenic rice lines carrying ENOD4O and GS5O genes to study the signal transduction chain in rice during the interactions with rhizobia.


 

Acknowledgement
Financial supports from the Rockefeller Foundation, NY and DANIDA, Denmark are gratefully acknowledged.
References
Charon, C., C. Johansson. E. Kondorosi, A. Kondorosi and M. Crespi, 1997. ENOD4O induces dedifferentiation and division of root cortical cells in legumes. PNAS 94: 8901-8906.
Mylona, P., K. Pawlowski and T. Bisseling, 1995. Symbiotic nitrogen fixation. Plant cell 7: 869-885.
Papadopoulou, K., A. Roussis and P. Katinakis, 1996. Phaseolus ENOD4O is involved in symbiotic and non- symbiotic organogenetic processes: expression during nodule and lateral root development. Plant Mol. Biol. 30: 403-417.
Kouchi, H., K. Takane, R.B. So, J.K. Ladha and P.M. Reddy, 1999. Rice ENOD4O Isolation and Expression
Analysis in Rice and Transgenic Soybean Root Nodules. Plant J. 18: 121-129.
Eztler, M.E., G. Kalsi, N.N. Ewing, N.J. Roberts, R.B. Day and J.B. Murphy, 1999. A nod factor binding lectin with apyrase activity from legume roots. PNAS USA 96: 5856-5861