Polyamine interactions with plant hormones: crosstalk at several levels

Authors: ANWAR, RAHEEL - Purdue University; Mattoo, Autar; HANDA, AVTAR - Purdue University

Submitted to: Springer Verlag
Publication Type: Book / Chapter
Publication Acceptance Date: 8/22/2014
Publication Date: 2/20/2015
Citation: Anwar, R., Mattoo, A.K., Handa, A. 2015. Polyamine interactions with plant hormones: crosstalk at several levels. In: Kusano, T., Suzuki, H., editors. Polyamines: A Universal Molecular Nexus for Growth, Survival and Specialised Metabolism. New York, NY: Springer Verlag. 22:267-302.

Interpretive Summary: Plants are sessile organisms and have acquired the ability to adapt to continuously changing environments. Perception of environmental clues is largely controlled by a few plant hormones: auxin, cytokinin, gibberellins, abscisic acid, ethylene, salicylic acid, brassinosteroids and jasmonates. However, it is now recognized that the plant response to environmental conditions is complex and orchestrated by a network of the equally complex crosstalk among plant hormones. Polyamines are biogenic amines that have recently re-emerged as important plant growth and development regulators via hard genetic evidence and biochemical studies. They play essential roles in both physiological and developmental processes. Although many plant cell processes are regulated by one or more plant hormones, little is understood about the crosstalk among plant hormones and biogenic amines. Our analysis of the transcriptomic data suggests a complex relationship among the biogenic amines, and their role(s) in the biosynthesis and signaling pathways of plant hormones. We have collated this information and present here models that provide a road map, which can be further modified and revised as more transcriptome, proteome and metabolome data become available. These studies are important to agricultural scientists, scientists working on the role of polyamines across kingdoms, and molecular biologists.

Technical Abstract: Polyamines play important roles in diverse plant growth and development processes including seed germination, tissue lignification, organogenesis, flowering, pollination, embryogenesis, fruit development, ripening, abscission, senescence and stress responses. In all these processes, synergistic and antagonistic interactions among various plant hormones have been shown. Although significant progress has been made in understanding the regulation of biosynthesis and signal transduction mechanisms for most of the plant hormones, inroads into the molecular mechanisms underlying polyamine (PA) action have just begun. Little is known or understood about the signal transduction pathways regulating a myriad of PA effects. We, therefore, embarked on evaluating and collating the information on changes in the transcriptome based on metabolic engineering of PA pathway as well as mutants of PA biosynthesis. Also taken into consideration are the studies using exogenous application of PAs. Our analysis has revealed complex and differential relationships among the three main PAs - putrescine, spermidine and spermine, in regard to regulation of plant hormone biosynthesis and signaling. Putrescine is positively linked to the expression of genes regulating ABA biosynthesis but downregulates those of ethylene, jasmonates and gibberellins biosynthesis, and exactly opposite was found to be the action of spermidine. Spermine, on the other hand, enhanced genes for ethylene and jasmonates biosynthesis but downregulated those for gibberellins and abscisic acid biosynthesis. In regard to hormone signaling pathways, spermidine positively regulated salicylic acid signaling genes and those of auxin and cytokinins signaling genes were linked to spermine action. Putrescine was neutral to positive in regulating jasmonates signaling. PAs seem to be neutral in regard to brassinosteroids biosynthesis and/or signaling pathways.