Achievements

Major areas of research include:
(i) Novel plant genes and regulation of their expression
(ii) Signal transduction and photobiology,
(iii) Transgenics for crop improvement,
(iv) Stress molecular biology,
(v) Plant biotechnology for human health, and
(vi) Rice genomics.
The research in all these above areas requires characterization of genes or regulatory elements and development of transgenics to define function of new genes/elements or engineer genes for crop improvement. Several genes have been isolated/identified by screening cDNA/genomic libraries of indica rice, wheat and Arabidopsis, which specifically or abundantly express in leaf (PSBO, PSBP, PSBQ), root (OsiMFP, encoding a multifunctional protein), inflorescence (OsiPK and OsiPA, encoding a protein kinase and a pollen-specific allergen), two genes for putative transcription factors, OsiIAA1 and OsiSAP (one auxin-inducible and the other stress-inducible with a Zn++ finger motif), seven photoreceptor or phototransduction component genes (OsiNPH1, OsiCRY2, OsiCOP1, PHYA-1, PHYA-2, PHYC, POLYROSETTA), two genes for putative methylated DNA-binding proteins, and several heat shock protein genes. Other genes are likely to be isolated, as proteomics approach has already yielded information about proteins accumulating in response to abiotic stresses. In addition, a novel method for isolation of flanking regions from the known sequences has been developed which has potential significance in studying regulation of gene expression. India decided to participate in the International Rice Genome Sequencing Programme (IRGSP) in the year 2000 and made commitment to sequence about >10 Mb in the long arm of rice chromosome 11 (from 56.9 to 115.2 cM). One group at Delhi University South Campus and another at IARI, New Delhi, are engaged in this venture. To begin with, efforts were made to screen a PAC library and two BAC libraries by using genetic markers and ESTs. This has helped in generating a minimum tiling path for about 85% of the region assigned to India. Based upon this information, at least 56 PAC/BAC clones were selected for sequencing and analysis at South Campus. Already sequencing and assembly of 45 BAC/PAC clones, assigned to South Campus, has been completed. By performing >200,000 sequencing reaction, about 100 Mb data has been generated leading to assembled sequence of ~ 6.6 Mb at >10X level. Out of this, >6 Mb data has been released. For details, one can visit our web-site www.genomeindia.org.in.

Some basic studies on how light regulated plant growth and development constitutes another ongoing research programme in the Department. Although studies may sound more of fundamental nature, but understanding how light controls the process of seed germination, plant height, leaf/canopy architecture and, more so, the flowering time and leaf senescence will be of utmost importance for manipulating these processes vital for greater harvest index. The experimental material of choice for these studies has been primarily Arabidopsis and, lately, the work is also extended to wheat, rice and Brassica. Several mutants of Arabidopsis that display constitutive photomorphogenesis in dark, and flower precociously have been isolated. Some other mutants are dwarf in nature but yet retain normal silique size. Molecular genetic analysis of these mutants is being done to map the loci and design strategies for cloning the corresponding genes. In the past few years, it has become abundantly clear that, like the red/far-red light sensing phytochrome, blue light is also perceived by a small family of sensory photoreceptors, which include CRY1, CRY2, PHOT1 and PHOT2. Both CRY1 and CRY2 genes have been sequenced from Brassica and rice, respectively. At present, vectors are being constructed to engineer these genes in crops like rice (a monocot) and Brassica (a dicot) to control traits like flowering time and plant height. Transgenic systems of indica rice and wheat have been developed in addition to Arabidopsis and tobacco. While rice has been transformed with codA/COR47, AtHSP100 and PDC genes, wheat has been transformed with HVA1 to confer stress tolerance. In addition, wheat has been transformed with PINII (for insect resistance). This required a better understanding and control of regeneration process via somatic embryogenesis as well as construction of new transformation vectors. All transgenics have been characterized at the molecular level for gene integration and expression at mRNA and protein levels. In several cases, inheritance of the gene has been followed in more than one generation and, in some cases, improvement in stress tolerance has been checked at the seedling stage. With the view of developing edible vaccine against cholera, work has been carried out to raise transgenic tomato/tobacco expressing non-pathogenic cholera toxin submit B and a anti-colonization protein, TCP. These plants have been analyzed at molecular and immunological level. In order to have a better understanding of the functional interactions between plant and pathogens, two important agricultural pathogens of India have been chosen, rice tungro virus and Indian cassava mosaic virus. The entire genome of the rice tungro bacilliform virus, one of the members of the two-component rice tungro virus complex, has been completely sequenced and analyzed from two geographically distant locations of our country and shown to be having a genetic composition distinct from those from southeast Asian region. However, within the country, the viral genes, namely those coding for the capsid protein and movement protein were highly conserved in more than six different field isolates examined. Transgenic viral resistance in rice is being investigated by using the capsid protein gene, antisense genes and RNA-interference. The viral promoter has been functionally characterized. Various interacting host proteins from rice are being characterized to understand the development of pathogenesis in this disease. A similar approach has been adopted to characterize genes from cassava, which show differential expression, following infection with cassava mosaic virus.

The above research work has reached a critical level for embarking on the path of functional validation and application. While organ-specific genes provide a mean to obtain target-specific regulatory elements, several of them have potential to provide tools for crop improvement for agronomically important traits like stress tolerance or plant architecture, including seedling height and flowering time. Novel stress-inducible proteins and antisera raised against them should help in isolation of more useful genes.

Thus, the function of gene regulatory elements and the useful genes isolated is being evaluated by molecular and transgenic approach, efficient protocols for which have been developed in case of rice, wheat, tomato Arabidopsis and tobacco. New constructs are being made with a view of gene stacking.

This would generate new products and intellectual property.

Professor A.K. Tyagi: Fellow, National Academy of Sciences, India Fellow, National Academy of Agriculture Fellow, Indian National Science Academy National Bioscience Award, DBT

Professor J.P. Khurana: Fellow, National Academy of Sciences, India.

Professor A. Grover: Fellow, National Academy of Sciences B.M. Birla Science Prize in Biology Professor Hiralal Chakravarthy Award (ISCA)

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