Anil Grover

Senior Professor (Superannuated)

Specializations: Hsp100 Proteins and Plant Heat Stress Biology


Research Interests

The threat of climate change to agriculture is showing its effects. For breeding plants with superior heat tolerance ability by genetic methods, it is important to decipher the cellular processes that contribute to plant heat tolerance. Hsp101/ClpB1 chaperone protein represents the protein disaggregation machinery of the cells. Hsp101 transcript/ protein are strongly upregulated by heat stress. Our work is focused on the following aspects of Arabidopsis and rice Hsp101 proteins: 

  1. We wish to understand the transcriptional basis of OsHsp101 (Os05g44340) induction under heat stress. Rice genome sequence has 25 OsHsf genes including 13 class A, 8 class B and 4 class C members. Yeast one-hybrid assays showed us that OsHsfA6a specifically interacts with OsHsp101 promoter. Using several deletion constructs, high transactivation potential of OsHsfA6a was mapped to its C-terminal domain. Role of post-translational modifications especially phosphorylation in regulating the activity of OsHsfA6a was highlighted. Interactors of OsHsfA6a were identified by library scale screening and are being analysed for their functional significance on OsHsp101 gene expression. 
  2. In respect of Arabidopsis Hsp101 (At1g74310), we noted that salk_087844 mutant (hx mutant) lacks expression of 6 tandem genes. The hx seedlings possess significantly higher basal thermotolerance as compared to wild type, Col-0 seedlings. hsc70-1 mutation emerged as the major player in causing higher basal thermotolerance phenotype of the hx line.  The complementation of hx mutant with Hsc70-1 genomic region rescued the Col-0 like phenotype while the over-expression of genome fragment of Hsc70-1 in Col-0 background resulted in higher sensitivity of the transgenic lines to heat stress. Hsp101 transcript and protein levels were conspicuously higher especially during non-heat stress and post-heat stress recovery conditions in hx seedlings. We propose that Hsc70-1 is a negative regulator affecting HsfA1d/A1e/A2 activators which in turn regulate Hsp101 expression and basal thermotolerance. 
  3. To optimize the genetic expression of Hsp101 in transgenic Arabidopsis plants for enhancing its heat tolerance phenotype, four constructs made were CaMV35 promoter driven AtHsp101 cDNA (CaMV35S:AtHsp101construct), CaMV35S promoter driven OsHsp101 cDNA (CaMV35S:OsHsp101 construct), AtHsp101 promoter driven-OsHsp101 cDNA (AtHsp101p:OsHsp101construct) and with AtHsp101 genome fragment  (AtHsp101-genomic fragment construct). Wild type (WT) Arabidopsis plants transformed with CaMV35S:OsHsp101 construct (C lines) showed equal or more sensitive phenotype under HS than the WT seedlings. Hsp101 protein levels were mostly lower in transgenic C lines than the WT seedlings. Under HS, WT Arabidopsis plants transformed with AtHsp101p:OsHsp101construct (IN lines) showed increased AtHsp101 transcript and protein amounts as well as higher heat tolerant phenotype of the seedlings as against the WT seedlings. In case of WT Arabidopsis plants transformed with AtHsp101-genomic fragment construct (GF lines), two kinds of progenies were noted. Most lines (11 out of 14) showed over-expression of AtHsp101 transcript and protein and showed more heat tolerant phenotype than the WT seedlings. Hsp101 transcript and protein in 3 lines out of 14 (GF3-5, GF7-3 and GF53-6 lines) were drastically impaired, and these lines were overly sensitivity to HS. 
  4. Allele sequencing and gene polymorphism provide the needed inputs for the development of functional molecular markers for the marker-assisted selection approach. The intraspecific variation in Hsp101 expression has been observed in Arabidopsis as well as in rice. In this respect, finding genetic variations in the regulatory regions controlling the Hsp101 expression as well as those affecting Hsp101 disaggregase activity will be greatly pertinent. We noted 63 allelic forms of Hsp101 in 855 accessions of Arabidopsis. With have likewise identified Hsp101 allelic forms in rice thanks to the availability of genomic sequences for more than 3000 rice types. We believe that harnessing sequence variability of Hsp100s and phenotyping of crop germplasm will advance our understanding of plant response to high temperature stress as well as pave a way in gene pyramiding for breeding heat-tolerant crops.

 Select Publications

  1. Kumar R, Tripathi G, Goyal I, Sharma J, Tiwari R, Shimphrui R, Sarkar NK, Grover A (2023). Insights into genomic variations in rice Hsp100 genes across diverse rice accessions. Planta 257(5):91. DOI: 10.1007/s00425-023-04123-1
  2. Kumar R, Ghatak A, Goyal I, Sarkar NK, Weckwerth W, Grover A, Chaturvedi P (2023). Heat-induced proteomic changes in anthers of contrasting rice genotypes under variable stress regimes. Frontiers in Plant Science 13:1083971. DOI: 10.3389/fpls.2022.1083971
  3. Babbar R, Tiwari LD, Mishra RC, Shimphrui R, Singh AA, Goyal I, Rana S, Kumar R, Sharma V, Tripathi G, Khungar L, Sharma J, Agrawal C, Singh G, Biswas T, Biswal AK, Sahi C, Sarkar NK, Grover A (2023). Arabidopsis plants overexpressing additional copies of heat shock protein Hsp101 showed high heat tolerance and endo-gene silencing. Plant Science 330:111639. DOI: 10.1016/j.plantsci.2023.111639
  4. Singh G, Banerjee G, Sarkar NK, Sinha AK, Grover A (2022). Transcriptional regulation of rice HSP101 promoter: Mitogen-activated protein kinase-mediated HSFA6a phosphorylation affects its stability and transactivation. Physiologia Plantarum 174(4):e13754. DOI: 10.1111/ppl.13754
  5. Tiwari LD, Kumar R, Sharma V, Sahu AK, Sahu B, Naithani SC, Grover A (2021). Stress and development phenotyping of Hsp101 and diverse other Hsp mutants of Arabidopsis thaliana. J. Plant Biochemistry Biotechnology 30:889–905. DOI: 10.1007/s13562-021-00706-9
  6. Singh G, Sarkar NK, Grover A (2021). Hsp70, sHsps and ubiquitin proteins modulate HsfA6a-mediated Hsp101 transcript expression in rice (Oryza sativa L.). Physiologia Plantarum 173(4):2055–2067. DOI: 10.1111/ppl.13552
  7. Singh G, Sarkar NK, Grover A (2021). Tango between Ethylene and HSFA2 settles heat tolerance. Trends in Plant Science 26(5):429–432. DOI: 10.1016/j.tplants.2021.03.003
  8. Babbar R, Karpinska B, Grover A, Foyer CH (2021). Heat-induced oxidation of the nuclei and cytosol. Frontiers in Plant Science 11:617779. DOI: 10.3389/fpls.2020.617779
  9. Kumar R, Khungar L, Shimphrui R, Tiwari LD, Tripathi G, Sarkar NK, Agarwal SK, Agarwal M, Grover A (2020). AtHsp101 research sets course of action for the genetic improvement of crops against heat stress. J. Plant Biochemistry and Biotechnology 29:715–732. DOI: 10.1007/s13562-020-00624-2
  10. Tiwari LD, Khungar L, Grover A (2020). AtHsc70-1 negatively regulates the basal heat tolerance in Arabidopsis thaliana through affecting the activity of HsfAs and Hsp101. Plant J. 103(6):2069–2083. DOI: 10.1111/tpj.14883
  11. Sarkar NK, Kotak S, Agarwal M, Kim YK, Grover A (2020). Silencing of class I small heat shock proteins affects seed-related attributes and thermotolerance in rice seedlings. Planta 251(1):26. DOI: 10.1007/s00425-019-03318-9
  12. Lavania D, Dhingra A, Grover A (2018). Analysis of transactivation potential of rice (Oryza sativa L.) heat shock factors. Planta 247(6):1267–1276. DOI: 10.1007/s00425-018-2865-2.
  13. Singh G, Sarkar NK, Grover A (2018). Mapping of domains of heat stress transcription factor OsHsfA6a responsible for its transactivation activity. Plant Science 274:80–90. DOI: 10.1016/j.plantsci.2018.05.010
  14. Mishra RC, Grover A (2016). ClpB/Hsp100 proteins and heat stress tolerance in plants. Critical Reviews Biotechnology 36(5):862–874. DOI: 10.3109/07388551.2015.1051942
  15. Mishra RC, Grover A (2014). Intergenic sequence between Arabidopsis caseinolytic protease B-cytoplasmic/heat shock protein100 and choline kinase genes functions as a heat-inducible bidirectional promoter. Plant Physiology 166(3):1646–1658. DOI: 10.1104/pp.114.250787
  16. Sarkar NK, Kim YK, Grover A (2014). Coexpression network analysis associated with call of rice seedlings for encountering heat stress. Plant Molecular Biology 84(1–2):125–143. DOI: 10.1007/s11103-013-0123-3
  17. Singh A, Singh U, Mittal D, Grover A (2010). Genome-wide analysis of rice ClpB/HSP100, ClpC and ClpD genes. BMC Genomics 11:95. DOI: 10.1186/1471-2164-11-95
  18. Singh A and Grover A (2010). Plant Hsp100/ClpB-like proteins: poorly-analyzed cousins of yeast ClpB machine. Plant Molecular Biology 74: 395–404. DOI:10.1007/s11103-010-9682-8.
  19. Sarkar NK, Kim Y-K, and Grover A (2009). Rice sHsp genes: genomic organization and expression profiling under stress and development. BMC Genomics 10:393. DOI: 10.1186/1471-2164-10-393
  20. Katiyar-Agarwal S, Agarwal A, and Grover A (2003). Heat-tolerant basmati rice engineered by over-expression of hsp101 gene. Plant Molecular Biology 51: 677–686. DOI: 10.1023/A:1022561926676
  21. Agarwal M, Sahi C, Katiyar-Agarwal S, Agarwal S, Young T, Gallie DR, Sharma VM, Ganesan K, and Grover A (2003). Molecular characterization of rice hsp101: complementation of yeast hsp104 mutation by disaggregation of protein granules and differential expression in indica and japonica rice types. Plant Molecular Biology 51(4):543–553. DOI: 10.1023/a:1022324920316
  22. Agarwal M, Katiyar-Agarwal S, Sahi C, Gallie DR, and Grover A (2001). Arabidopsis thaliana Hsp100 proteins: kith and kin. Cell Stress Chaperones 6(3):219–224.
  23. Singla SL, Pareek A, Kush AK, and Grover A (1998). Distribution patterns of 104 kDa stress-associated protein in rice. Plant Molecular Biology 37(6):911–919. DOI: 10.1023/a:1006099715375
  24. Pareek A, Singla SL, and Grover A (1995). Immunological evidence for accumulation of two high-molecular-weight (104 and 90 kDa) HSPs in response to different stresses in rice and in response to high temperature stress in diverse plant genera. Plant Molecular Biology 29(2):293–301. DOI: 10.1007/BF00043653
  25. Singla SL and Grover A (1993). Antibodies raised against yeast HSP 104 cross-react with a heat- and abscisic acid-regulated polypeptide in rice. Plant Molecular Biology 22(6):1177–1180. DOI: 10.1007/BF00028989