Plant ABC Transporters
editThe genome of the model plant Arabidopsis thaliana is capable of encoding 120 ABC proteins compared to 50-70 ABC proteins that are encoded by the human genome and fruit flies (Drosophila melanogaster). Plant ABC proteins are categorized in 13 subfamilies on the basis of size (full, half or quarter), orientation, and overall amino acid sequence similarity[1]. Multidrug resistant (MDR) homologs, also known as P-glycoproteins, represent the largest subfamily in plants with 22 members and the second largest overall ABC subfamily. The B subfamily of plant ABC transporters (ABCBs) are characterized by their localization to the plasma membrane. Plant ABCB transporters are characterized by heterologously expressing the them in Escherichia coli, Saccharomyces cerevisiae, Schizosaccharomyces pombe (fission yeast), and HeLa cells to determine substrate specificity. Plant ABCB transporters have shown to transport the phytohormone indole-3-acetic acid ( IAA), also known as auxin, the essential regulator for plant growth and development[2]. The directional polar transport of auxin mediates plant environmental responses through processes such as phototropism and gravitropism [3]. Two of the best studied auxin transporters, ABCB1 and ABCB19, have been characterized to be primary auxin exporters. Other ABCB transporters such as ABCB4 participate in both the export and import of auxin. At low intracellular auxin concentrations ABCB4 imports auxin until it reaches a certain threshold which then reverses function to only export auxin[4].
References
edit- ^ Rea, Philip A. (2007). "Plant ATP-Binding Cassette Transporters". Annual Review of Plant Biology. 58 (1): 347–375. doi:10.1146/annurev.arplant.57.032905.105406. ISSN 1543-5008.
- ^ Yang, Haibing; Murphy, Angus S. (2009). "Functional expression and characterization of Arabidopsis ABCB, AUX 1 and PIN auxin transporters inSchizosaccharomyces pombe". The Plant Journal. 59 (1): 179–191. doi:10.1111/j.1365-313X.2009.03856.x. ISSN 0960-7412.
- ^ Kretzschmar, Tobias; Burla, Bo; Lee, Youngsook; Martinoia, Enrico; Nagy, Réka (2011). "Functions of ABC transporters in plants". Essays in Biochemistry. 50 (1): 145–160. doi:10.1042/bse0500145. ISSN 0071-1365.
- ^ Kubeš, Martin; Yang, Haibing; Richter, Gregory L.; Cheng, Yan; Młodzińska, Ewa; Wang, Xia; Blakeslee, Joshua J.; Carraro, Nicola; Petrášek, Jan; Zažímalová, Eva; Hoyerová, Klára; Peer, Wendy Ann; Murphy, Angus S. (2012). "The Arabidopsis concentration-dependent influx/efflux transporter ABCB4 regulates cellular auxin levels in the root epidermis". The Plant Journal. 69 (4): 640–654. doi:10.1111/j.1365-313X.2011.04818.x. ISSN 0960-7412.