Datta1*
3127, 1271 Makati City, Philippines
City, Philippines
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 |