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Research Interests

Our main research focus areas come under physiological and molecular aspects of the regulation of vegetative development of plants. We use rice, Arabidopsis and the mangrove tree Avicennia officinalis for our experiments.

Our recent findings on plant hormone signaling (with special focus on gibberellins and abscisic acid) and shoot development led to the discovery of a genetic pathway in the gibberellin signalling (RGL2-DOF6 protein complex inducing the expression of GATA12 gene) that affects primary seed dormancy. Funding for this work came from the National Research Foundation (NRF), Singapore as part of a collaborative research project aimed at improving the rice crop. We are currently studying various gibberellin signal transduction intermediates in the regulation of seed germination and related processes. Molecular characterization of selected new mutants of rice that show changes in agronomic traits is in progress. The traits of interest include seedling vigor, salt tolerance and seed yield.

Another major research interest in our lab is to understand the salt secretion and salt ultrafiltration mechanisms in the mangrove tree Avicennia officinalis. We are focusing on aquaporins and ion transporters from the mangrove and designing synthetic pores that can be used for biomimetic membrane preparation. We are also attempting to apply the molecular mechanisms discovered to crop plants such as rice and impart salinity tolerance to these species. This work is funded by the Singapore National Research Foundation under its Environment and Water Research Program and administered by PUB, Singapore’s National Water Agency.

Besides helping to gain a better understanding of plant development, we hope that our work can contribute towards crop improvement in the long-term.

Research Accomplishments

We have identified several genes that are over expressed or are activated specifically during shoot bud differentiation in plant tissue cultures. We are carrying out functional analysis of the isolated genes using a transgenic plant approach.

We have devised a novel, PCR-based strategy coupled with lambda exonuclease (l-Exo strategy) to generate single-stranded cDNA suitable for subtractive hybridization. One of the genes we isolated using l-Exo strategy codes for a bZIP transcription factor and it is over expressed by about 6-fold in the shoot-forming leaf cultures of Paulownia.

Another cDNA we have isolated (PkMADS) from shoot-forming leaf cultures of Paulownia kawakamii encodes for a MADS-box protein. This gene is expressed only in the shoot-forming cultures and in the shoot apex, and not in the leaves, callus, the root apex or flowers. PkMADS has high homology (80-90%) to other MADS-box genes expressed in the vegetative tissues (e.g., SVP of Arabidopsis). Antisense suppression of this gene resulted in significant changes in phenotype – the transgenic Paulownia shoots were stunted, had altered venation and phyllotaxy and in some lines the shoot apical meristem was used up early during shoot development. Also, leaf explants from the antisense transgenic plants showed tenfold decrease in shoot regeneration than the explants from the sense transformants. These results clearly indicate that the isolated vegetatively expressed MADS box gene is involved in regulating vegetative shoot development in Paulownia kawakamii.

A gene for cytokinin-binding protein we have cloned from petunia has high homology to S-adenosyl homocysteine hydrolase from several sources including humans. We have succeeded in building an iterative model for this protein based on the homology. This protein has distinct nucleotide-binding domains, which may serve as cytokinin-binding domains in plants. Antisense suppression of this gene resulted in excessive branching and delayed flowering phenotype in about 50% of the lines. Additionally, the leaf explants from such transgenic petunia plants showed significant reduction in adventitious shoot regeneration. This gene can be a candidate for biotechnological manipulation of leafy vegetable species

Current Projects

Our current research projects come under the following themes:

1. Cloning genes that regulate primary seed dormancy and plant development.
2. Phytohormone (gibberellin & abscisic acid) signaling intermediates and plant development.
3. Transgenic plants for functional analysis of selected cDNA.
4. Mechanism of salt secretion in the mangrove Avicennia officinalis.
5. Synthesis of pores for water and ion transport on biomimetic membranes.

Research Accomplishments

Full List of Publications

Membership on Editorial Boards

1. Editor, BMC Plant Biology, (from Jan 2015)
2. Editor, Plant Cell Reports (Springer, from Jan 1999)
3. Associate Editor, Plant Biotechnology Reports (Springer, from Nov 2009)
4. Editor, Plant Biotechnology Reports (Springer, April 2007-Nov 2009)
5. Reviews Editor, Plant Cell Reports (Springer, from April 2002 – Nov 2008)
6. Editor, Plant Cell, Tissue and Organ Culture – (Jan 1999 – Jan 2006)
7. Review Editor, Frontiers in Plant Science (Oct 2014 – Oct 2016)

 

Selected Publications

1. Ravindran P, Kumar PP. Regulation of seed germination: The involvement of multiple forces exerted via gibberellic acid signalling. Mol Plant (2019) 12: 24-26.

2. Vishal B, Krishnamurthy P, Ramamoorthy R, Kumar PP. OsTPS8 controls yield-related traits and confers salt stress tolerance in rice by enhancing suberin deposition. New Phytologist 221: 1369–1386 (doi: 10.1111/nph.15464).

3. Ravindran P, Verma V, Stamm P, Kumar PP. A novel RGL2-DOF6 complex contributes to primary seed dormancy in Arabidopsis thaliana by regulating a GATA transcription factor. Molecular Plant (2017) http://dx.doi.org/10.1016/j.molp.2017.09.004.

4. Verma V, Sivaraman J, Srivastava AK, Sadanandom A, Kumar PP. Destabilization of interaction between cytokinin signaling intermediates AHP1 and ARR4 modulates Arabidopsis development. New Phytologist (2015) 206: 726–737 doi: 10.1111/nph.13297

5. Krishnamurthy P, Jyothi-Prakash PA, Lin Qin, He J, Lin Q, Loh CS, Kumar PP. Role of root hydrophobic barriers in salt exclusion of a mangrove plant Avicennia officinalis. Plant, Cell & Environment(2014) 37:1656–1671.

6. Kohli A, Sreenivasulu N, Lakshmanan P, Kumar PP. The phytohormone crosstalk paradigm takes center stage in understanding how plants respond to abiotic stresses. Plant Cell Reports (2013) 32:945-957 DOI: 10.1007/s00299-013-1461-y

7. Tan W-K, Lin Q, Lim TM, Kumar PP, Loh CS. Dynamic secretion changes in the salt glands of the mangrove tree species Avicennia officinalis in response to a changing saline environment. Plant, Cell & Environment (2013) 36:1410-1422. DOI: 10.1111/pce.12068

8. Stamm P, Ravindran P, Mohanty B, Tan EL, Yu H, Kumar PP. Insights into the molecular mechanism of RGL2-mediated inhibition of seed germination in Arabidopsis thaliana. BMC Plant Biology (2012) 12:179 doi:10.1186/1471-2229-12-179 (http://www.biomedcentral.com/1471-2229/12/179).

9. Stamm P, Kumar PP. The phytohormone signal network regulating elongation growth during shade avoidance. Journal of Experimental Botany (2010) 61: 2889-2903.

10. Xu Y, Teo LL, Zhou J, Kumar PP, Yu H. Floral organ identity genes in the orchid Dendrobium crumenatum. Plant Journal (2006) 46: 54-68.

11. Yu H, Ito T, Zhao Y, Peng J, Kumar PP, Meyerowitz EM. Floral homeotic genes are targets of gibberellin signaling in flower development. Proc. Natl. Acad. Sci., USA (2004) 101:7827-7832.

12. Zhang P, Pwee KH, Tan HT, Kumar PP. Conservation of class C function of floral organ development during 300 million years of evolution from gymnosperms to angiosperms. Plant Journal (2004) 37: 566-577.

13. Yu H, Xu Y, Tan EL, Kumar PP. 2002. AGAMOUS-LIKE 24, a dosage-dependent mediator of the flowering signals. Proc. Natl. Acad. Sci., USA. 99:16336-16341.

14. Prakash AP, Kumar PP. 2002. PkMADS1 is a novel MADS-box gene regulating adventitious shoot induction and vegetative shoot development in Paulownia kawakamii. Plant Journal 29:141-151.