We have long been involved in elucidating the metabolic pathways for both biosynthesis and degradation of several acyclic sugar alcohols, e.g., sorbitol and mannitol, and determining the characteristics and tissue, cell, and subcellular locations of those enzymes involved in these pathways. Enzyme identification and characterization currently includes study of regulatory mechanisms at both the protein and gene level. We have, for example, cloned and sequenced the gene for mannose 6-phosphate reductase, a key step in mannitol biosynthesis, and are now investigating those factors involved in its regulation. Similar work is focused on sugar alcohol transporters.
We are very interested in developing an understanding of the mechanisms by which plants tolerate abiotic stress, environmental extremes such as salinity, drought, and temperature, especially since several of these mechanisms may be related to the capacity of some plants to synthesize compatible solutes like the acyclic sugar alcohols. Accordingly, we have been looking at how certain abiotic stresses regulate sugar alcohol metabolism, storage, and transport, and how these compounds may accumulate in response to exposure to stress.
Carbohydrate partitioning and photosynthesis
In collaboration with colleagues we have been involved in a variety of projects related to determining patterns of carbohydrate allocation as a result of sink/source interactions. These interactions profoundly affect crop quality and yield, yet little is known about the mechanisms involved.
G. Song, A.E. Walworth, W. Loescher. 2015. Grafting of genetically engineered plants. J. Amer. Soc. Hort. Sci. 140:203-213.
J. Everard, W. Loescher. 2015. Photosynthesis and partitioning: primary products of photosynthesis, sucrose and other soluble carbohydrates, Encyclopedia of Applied Plant Sciences, 2nd edition. J. Harbinson, ed. Elsevier
W. Loescher 2015. Cherries. Encyclopedia of Food and Health, Elsevier In Press
G. Mukeshimana, A.L. Lasley, W.H. Loescher, J.D. Kelly 2014. Identification of shoot traits related to drought tolerance in common bean seedlings. J. Amer. Soc. Hort. Sci. 139:299-309
N.S. Jaikumar, S.S. Snapp, J.A. Flore, W. Loescher 2014. Photosynthetic responses in annual rye, perennial wheat, and perennial rye subjected to modest source:sink ratio changes. Crop Science 54:274-283
T.X. Nguyen, T. Nguyen, H. Alameldin, B. Goheen, W. Loescher, M. Sticklen, 2013. Transgene pyramiding of the HVA1 and mtlD in T3 maize (Zea mays L.) plants confers drought and salt tolerance, along with an increase in crop biomass. International J. Agron. Vol. 2013, Article ID 598163, 10 pages, 2013. doi:10.1155/2013/598163
Z. Chan, W. Loescher, R. Grumet 2013. Transcriptional variation in response to salt stress in commonly used Arabidopsis thaliana accessions. Plant Physiology and Biochemistry 73:189-201
Y. Wang, L. Yang, Z. Zheng, R. Grumet, W. Loescher, J.-K. Zhu, P. Yang, Y. Hu, Z. Chan. 2013. Transcriptomic and physiological variations of three Arabidopsis ecotypes in response to salt stress. PLoS ONE 8(7): e69036. doi:10.1371/journal.pone.0069036
L. Wang, M.Xu, C. Liu, J. Wang, H.Xi, B. Wu, W. Loescher, W. Duan, P. Fan, S.-H. Li 2013. Resveratrols in grape berry skins and leaves in Vitis germplasm. PLoS ONE 8(4): e61642. doi:10.1371/journal.pone.0061642
Z. Chan, P. J. Bigelow, W. Loescher, R Grumet 2012, Global transcriptome profiling is a poor predictor of the secondary effects of transgenes influencing abiotic stress tolerance Information Systems for Biotechnology •www.isb.vt.edu August 2012
Z. Chan, P. J. Bigelow, W.H. Loescher, R. Grumet. 2012. Comparison of salt stress resistance genes in transgenicArabidopsis thaliana indicates that extent of transcriptomic change may not predict secondary phenotypic or fitness effects. Plant Biotechnology J. 10:284-300
Z. Chan, R. Grumet, W.H. Loescher. 2011. Global gene expression analysis of transgenic, mannitol-producing and salt tolerant Arabidopsis thaliana indicates widespread changes in expression of abiotic- and biotic-stress related genes. J. Exp. Bot. 62 (12): 4079-4086.
W. Loescher, Z. Chan, R. Grumet. 2011. Options for developing salt-tolerant crops. HortScience 46 :1085-1092.
L Wang, L Fan, W Loescher,W Duan, J Cheng, G Liu,S Li 2010. Salicylic acid alleviates decreases in photosynthesis under heat stress and accelerates recovery in grapevine leaves BMC Plant Biology 10:34.
G.-Q. Song, K.C. Sink, Y. Ma, T. Herlache, J.F. Hancock. W. Loescher 2010. A novel mannose-based selection system for plant transformation using celery mannose-6-phosphate reductase gene Plant Cell Reports 29:2:163-172
L.J. Wang, W. Loescher, W. Duan, W.-D. Li, S.-H. Yang, S.-H. Li 2009. Heat acclimation induced acquired heat tolerance and cross adaptation in different grape cultivars: relationships to photosynthetic energy partitioning. Functional Plant Biology 36: 516-526.
C. M. Sickler, G. E. Edwards, O. Kiirats, Z. Gao, W. Loescher. 2007. Response of mannitol-producing Arabidopsis thaliana to abiotic stress. Functional Plant Biology 34: 382-391.
S.-H Yang, L.-J. Wang, S.-H. Li, W. Duan, W. H. Loescher, and Z. Liang. 2007. The effects of UV-B radiation on photosynthesis in relation to Photosystem II photochemistry, thermal dissipation and antioxidant defenses in winter wheat (Triticum aestivum L.) seedlings at different growth temperatures. Functional Plant Biology 34: 907-917.
Gao, Z., S. Jayanty, R. Beaudry, and W. Loescher. 2005. Watercore and sorbitol transporters in apple sink tissues: implications for fruit sugar accumulation and watercore development. J Amer Soc Hort Sci 130:2:261-268.
U.S. Patent No. 6, 416,985. Issued July 9, 2002. Title: DNA Encoding Mannose 6-Phosphate Reductase and Recombinants Produced Therefrom. Inventors: W.H. Loescher, J. Everard, and R. Grumet.
Gao, Z., L. Maurousset, R. Lemoine, S.-D. Yoo, S. van Nocker, and W. Loescher. 2003. Cloning, expression, and characterization of sorbitol transporters from developing sour cherry (Prunus cerasus) fruit and leaf sink tissues. Plant Physiol 131:1566-1575.
Loescher, W.H. 2003. Cherries. Encyclopedia of Food Sciences and Nutrition, 2nd Ed. Academic Press, London. pp. 1135-1140.
Gao, Z., and W.H. Loescher. 2003. Expression of a celery mannose 6-phosphate reductase in Arabidopsis thaliana enhances salt tolerance and induces biosynthesis of both mannitol and a mannitol dimer. Plant Cell and Environment 26: 275-283
S.-D. Yoo, Gao, Z., C. Cantini, W. Loescher, and S. van Nocker. 2003. Fruit ripening in sour cherry (Prunus cerasus): changes in expression of genes expressing expansins and other cell-wall-modifying enzymes. J Amer Soc Hort Sci 128: 16-22.
Gao, Z. and W.H. Loescher. 2000. NADPH supply and mannitol biosynthesis: characterization, cloning, and regulation of the nonreversible glyceraldehyde-3-phosphate dehydrogenase in celery leaves. Plant Physiology 124: 321-330.
Loescher, W.H. and J.D. Everard. 2000. Regulation of sugar alcohol biosynthesis. In: R.C. Leegood, T. D. Sharkey, and S. von Caemmerer, eds., Photosynthesis: physiology and metabolism. Kluwer Academic Pubs., Dordrecht, The Netherlands. pp. 275-299
Everard, J.D., C. Cantini, R. Grumet, J. Plummer, and W.H. Loescher. 1997. Molecular cloning of mannose 6-phosphate reductase and its developmental expression in celery. Plant Physiology 113:1427-1435.
Loescher, W.H., and J.D. Everard. 1996. Metabolism of carbohydrates in sinks and sources: sugar alcohols. In: E. Zamski and A. Schaffer, eds., Distribution of photoassimilates in plants and crops: source-sink relationships. Marcel Dekker, Inc.. New York. pp. 185-207.
Loescher, W.H., J.D. Everard, C. Cantini, and R. Grumet. 1995. Sugar alcohol metabolism in source leaves. In: M. Madore and W. Lucas, eds. Carbon Partitioning and Source-Sink Interactions in Plants, American Society of Plant Physiologists, Rockville, MD. pp. 170-179.
Everard, J.D., R. Gucci, S.C. Kann, J.A. Flore, and W.H. Loescher. 1994. Gas exchange and carbon partitioning in the leaves of celery (Apium graveolens L.) at various levels of root zone salinity. Plant Physiol. 106:281-292.
Everard, J.D., V.R. Franceschi, and W.H. Loescher. 1993. Mannose-6-phosphate reductase, a key enzyme in photoassimilate partitioning, is abundant and located in the cytosol of photosynthetically active cells of celery (Apium graveolens L.) source leaves. Plant Physiol. 102:345-356.