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Professor, BIO5 Institute
Professor, Environmental Science
Professor, Plant Sciences
Martha Hawes is well known for her work on root border cells. Her entire career has focused on changing this perception and now border cells are described in numerous botany textbooks. Dr. Hawes has been very creative in designing experiments to understand the basic biology of this unique cell type especially in light of how border cells fight plant disease. Considering that the root tip serves as one of the major sources of root exudates that can attract microbial pathogens, the fact that this exceptionally vulnerable region of the root is protected from infection by the border cells is a real paradigm shift, especially via the mechanism.
Martha Hawes, PhD, realizes plants of many species systematically shed thousands of healthy cells from each of their root tips daily. Because these cells provide a living interface between the root and the soil, scientists refer to them as root "border" cells. This seemingly wasteful release of living somatic cells into environment is unique among higher organisms, and its function is unknown. Dr. Hawes’ hypothesis is that border cells provide a selective advantage to the plant by releasing specific chemicals that regulate levels of root- associated microorganisms. Soil-borne bacteria and fungi comprise not only pathogens that can destroy roots but also beneficial organisms that are crucial for normal plant development, therefore regulating the balance of such microbial populations is crucial to survival. Border cells act as a reservoir of chemicals that can specifically attract or repel microorganisms, as well as activate microbial genes headed for root infection. Mutants of soil-borne microorganisms have been used to demonstrate that, in some cases, recognition of such chemicals from the cells is required for the establishment of root-microbe associations. Her lab has identified border cell- specific genes cell as well as genes that are expressed among separation of border cells from the root. These plant genes are being used to genetically engineer plants with specific alterations in the production of border cells, and in their biological properties. These transgenic plants can be used test the hypothesis that border cells control the susceptibility of plants to infection by symbiotic and pathogenic bacteria and fungi.
Hawes, M. C., Huskey, D. A., Rivera, G. C., Chorover, J., Root, R., & Amistadi, M. K. (2017). Trapping of lead (Pb) by corn and pea root border cells. Plant and Soil, 10.
First description of the levels of toxins that can be removed by border cell trapping.
Hawes, M. C., Curlango-Rivera, G., Cho, I., Huskey, D., & Xiong, Z. (2014). Signals Controlling Extracellular Trap Formation in Plant and Animal Immune Responses. . Clinical Microbiology 3: 5-.. Clinical Microbiology, 3(5), 8-10.
Woo, H., Brigham, L. A., & Hawes, M. C. (1995). Molecular cloning and expression of mRNAs encoding H1 histone and an H1 histone-like sequences in root tips of pea (Pisum sativum L.). Plant Molecular Biology, 28(6), 1143-1147.
Two cDNA clones representing mRNAs, highly expressed in pea root tips, were isolated by mRNA differential display. Ribonuclease protection analyses showed different patterns of expression of these two messages in several pea tissues. Sequence analysis showed that the first clone, PsH1b-40, has 100% homology with a previously isolated H1 histone cDNA, PsH1b. However, it has an additional 30 nt at the 3′ end which is absent in PsH1b, suggesting possible multiple polyadenylation sites in the same mRNA. The second clone, PsH1b-41, encodes a deduced 19.5 kDa protein of 185 amino acids with an isoelectric point of 11.5. The putative globular domain of the encoded protein showed 67-71% residue identity with globular domains of 28 kDa pea PsH1b H1 histone and Arabidopsis thaliana H1-1 H1 histone. It has 9 repeating motifs of (T/S)XXK. In the C-terminal domain, there are four lysine-rich repeating motifs of SXK(T/S)PXKKXK which may be involved in chromatin condensation and decondensation. Southern blot analysis of nuclear DNA shows that PsH1-41 belongs to a multigene family. © 1995 Kluwer Academic Publishers.
Cannesan, M., Gangneux, C., Lanoue, A., Hawes, M., Driouich, A., & VicreM, . (2011). Association between border cell responses and localized root infection by pathogenic Aphanomyces euteiches. ANNALS OF BOTANY, 108(3), 459-469.
Kanemoto, R. H., Powell, A. T., Akiyoshi, D. E., Regier, D. A., Kerstetter, R. A., Nester, E. W., Hawes, M. C., & Gordon, M. P. (1989). Nucleotide sequence and analysis of the plant-inducible locus pinF from Agrobacterium tumefaciens.. Journal of Bacteriology, 171(5), 2506-2512.
PMID: 2708311;PMCID: PMC209927;Abstract:
Several loci on the tumor-inducing plasmid from Agrobacterium tumefaciens were transcriptionally activated in the presence of wounded plant tissue or extracts. The inducible virulence loci were required for efficient tumor formation. In contrast, the plant-inducible locus pinF was not observed to be absolutely essential for virulence. Mutants in pinF showed an attenuated virulence on a variety of dicotyledonous hosts, and this attenuation became more pronounced with decreasing numbers of bacterial cells in the inoculum. The DNA sequence of a 5.5-kilobase region which included the pinF locus from the octopine-type tumor-inducing plasmid A6 was determined. Four open reading frames consistent with the observed transcription of pinF were observed. Two of the open reading frames, pinF1 and pinF2, coded for polypeptides with relative molecular weights of 47,519 (pinF1) and 46,740 (pinF2). A comparison of the amino acid sequences of pinF1 and pinF2 indicated that they were similar to each other and to known polypeptide sequences for cytochrome P-450 enzymes.