Plant Molecular and Cell Biology

My lab is currently investigating mechanisms that regulate telomerase activity in plants. We previously showed that the pattern of telomerase expression in plants is remarkably similar to the pattern seen in humans, despite fundamental differences in development between plants and animals. Telomerase is abundantly expressed in reproductive organs but is undetectable in most vegetative organs (Fitzgerald et al., 1996). Additionally, telomerase can be induced in leaves and other vegetative organs by exposure to exogenous auxin.

To isolate genes that regulate telomerase, we screened a large population of activation tagged lines of Arabidopsis thaliana, and found that several lines that ectopically express telomerase in leaves. The first line we characterized over-expressed a gene encoding a small zinc finger transcription factor we designated TELOMERASE ACTIVATOR 1 (Ren et al., 2004). This factor does not bind to the promoter for TERT, which encodes the catalytically active subunit of telomerase. Instead, it binds to and activates transcription of BT2, a gene encoding a component of a ubiquitin ligase (Ren et al., 2007). Our working model is that the BT2 ubiquitin ligase marks a telomerase repressor for destruction, thereby allowing expression of telomerase. Efforts in the lab are currently focused on identifying the presumed telomerase repressor protein and other proteins that interact with BT2.

1. Burch, J, Chin, M, Fontenot, BE, Mandal, S, McKnight, TD, Demuth, JP et al.. Wright was right: leveraging old data and new methods to illustrate the critical role of epistasis in genetics and evolution. Evolution. 2024;78 (4):624-634. doi: 10.1093/evolut/qpae003. PubMed PMID:38241518 PubMed Central PMC10964199.
2. Ji, W, Mandal, S, Rezenom, YH, McKnight, TD. Specialized metabolism by trichome-enriched Rubisco and fatty acid synthase components. Plant Physiol. 2023;191 (2):1199-1213. doi: 10.1093/plphys/kiac487. PubMed PMID:36264116 PubMed Central PMC9922422.
3. Irigoyen, S, Ramasamy, M, Misra, A, McKnight, TD, Mandadi, KK. A BTB-TAZ protein is required for gene activation by Cauliflower mosaic virus 35S multimerized enhancers. Plant Physiol. 2022;188 (1):397-410. doi: 10.1093/plphys/kiab450. PubMed PMID:34597402 PubMed Central PMC8774732.
4. Mandal, S, Ji, W, McKnight, TD. Candidate Gene Networks for Acylsugar Metabolism and Plant Defense in Wild Tomato Solanum pennellii. Plant Cell. 2020;32 (1):81-99. doi: 10.1105/tpc.19.00552. PubMed PMID:31628166 PubMed Central PMC6961621.
5. Misra, A, McKnight, TD, Mandadi, KK. Bromodomain proteins GTE9 and GTE11 are essential for specific BT2-mediated sugar and ABA responses in Arabidopsis thaliana. Plant Mol Biol. 2018;96 (4-5):393-402. doi: 10.1007/s11103-018-0704-2. PubMed PMID:29363002 .
6. Góngora-Castillo, E, Childs, KL, Fedewa, G, Hamilton, JP, Liscombe, DK, Magallanes-Lundback, M et al.. Development of transcriptomic resources for interrogating the biosynthesis of monoterpene indole alkaloids in medicinal plant species. PLoS One. 2012;7 (12):e52506. doi: 10.1371/journal.pone.0052506. PubMed PMID:23300689 PubMed Central PMC3530497.
7. Robinson, WD, Park, J, Tran, HT, Del Vecchio, HA, Ying, S, Zins, JL et al.. The secreted purple acid phosphatase isozymes AtPAP12 and AtPAP26 play a pivotal role in extracellular phosphate-scavenging by Arabidopsis thaliana. J Exp Bot. 2012;63 (18):6531-42. doi: 10.1093/jxb/ers309. PubMed PMID:23125358 PubMed Central PMC3504502.
8. Mandadi, KK, Misra, A, Ren, S, McKnight, TD. BT2, a BTB protein, mediates multiple responses to nutrients, stresses, and hormones in Arabidopsis. Plant Physiol. 2009;150 (4):1930-9. doi: 10.1104/pp.109.139220. PubMed PMID:19525324 PubMed Central PMC2719139.
9. Shakirov, EV, McKnight, TD, Shippen, DE. POT1-independent single-strand telomeric DNA binding activities in Brassicaceae. Plant J. 2009;58 (6):1004-15. doi: 10.1111/j.1365-313X.2009.03837.x. PubMed PMID:19228335 PubMed Central PMC5880214.
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