Semagenesis and the parasitic angiosperm Striga asiatica

• Published in: The Plant journal : for cell and molecular biology Vol. 51; no. 4; pp. 707 - 716
• Main Authors: Keyes, William John, Palmer, Andrew G, Erbil, William Kaya, Taylor, Jeannette V, Apkarian, Robert P, Weeks, Eric R, Lynn, David G
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.08.2007; Blackwell Publishing Ltd; Blackwell Science
• Subjects: Agronomy. Soil science and plant productions; Biochemistry; Biochemistry and biology; Biological and medical sciences; Botany; Cellular biology; Chemical, physicochemical, biochemical and biological properties; Fundamental and applied biological sciences. Psychology; host-parasite relationships; host–parasite interactions; Hydrogen Peroxide - metabolism; Meristem - growth & development; Meristem - metabolism; Meristem - ultrastructure; Microscopy, Confocal; Microscopy, Electron, Transmission; Microscopy, Fluorescence; Parasites; parasitic angiosperms; Physics, chemistry, biochemistry and biology of agricultural and forest soils; Plant growth; reactive oxygen species; Reactive Oxygen Species - metabolism; Seedlings - growth & development; Seedlings - metabolism; Seedlings - ultrastructure; semagenesis; Soil science; Striga - growth & development; Striga - metabolism; Striga - ultrastructure; Striga asiatica; Time Factors; xenognosis; Root; xenognosis; Growth; semagenesis; Angiospermae; parasitic angiosperms; reactive oxygen species; Development; Spermatophyta; Striga asiatica; hostparasite interactions; Meristem
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/j.1365-313X.2007.03171.x

Over the last several years, intermediates in the reduction of dioxygen have been attributed diverse functional roles ranging from protection against pathogen attack to the regulation of cellular development. Evidence now suggests that parasitic angiosperms, which naturally commit to virulence through the growth of new organs, depend on reduced oxygen intermediates, or reactive oxygen species (ROS), for signal generation. Clearly, the role of ROS in both plant defense and other physiological responses complicates any models that employ these intermediates in host plant recognition. Here we exploit the transparent young Striga asiatica seedling to (i) localize the site of H₂O₂ accumulation to the surface cells of the primary root meristem, (ii) demonstrate the accumulation of H₂O₂ within cytoplasmic and apoplastic compartments, and (iii) document precise regulation of H₂O₂ accumulation during development of the host attachment organ, the haustorium. These studies reveal a new active process for signal generation, host detection and commitment that is capable of ensuring the correct spatial and temporal positioning for attachment.