Integrin-alpha-6+ Stem Cells (ISCs) are responsible for whole body regeneration in an invertebrate chordate

Colonial ascidians are the only chordates able to undergo whole body regeneration (WBR), during which entire new bodies can be regenerated from small fragments of blood vessels. Here, we show that during the early stages of WBR in Botrylloides diegensis, proliferation occurs only in small, blood-borne cells that express integrin-alpha-6 (IA6), pou3 and vasa. Ablation of proliferating cells using Mitomycin C (MMC) blocks WBR in vascular fragments, but can be rescued by injection of cycling cells isolated from an untreated individual. Using prospective isolation and limit dilution analyes, we found that FACS-isolated IA6+ stem cells (ISCs) could rescue WBR in MMC treated vascular fragments, even when injecting only a single cell. Lineage tracing using EdU-labeling further revealed that donor-derived ISCs directly give rise to regenerating tissues. Inhibitors of either Notch or canonical Wnt signaling block WBR and reduce proliferation of ISCs, indicating that these two pathways regulate ISC activation.

First Report of Glomerella cingulata on Common Guava in Argentina

In Argentina, common guava (Psidium guajava L.) is frequently planted in gardens, but commercial production is limited. In February 2001, anthracnose symptoms were detected on fruits of common guava in La Plata, Buenos Aires Province. Symptoms of grayish, circular, sunken spots approximately 5 cm long were observed only on the surface of green unripe fruits. In humid conditions, acervuli containing salmon-pink masses of spores and dark setae were found within lesions. Symptomatic tissue was surface-disinfested, placed on potato dextrose agar, and incubated at 20°C. Cultures were obtained with abundant, gray, aerial mycelium and one-celled, hyaline, oblong, or cylindrical conidia with rounded ends (9.7 to 14.5 × 3.2 to 5.2 μm). Scarce dark brown perithecia developed in 2-month-old cultures but were not observed on fruit tissues. Asci were not conspicuous and contained straight or slightly curved ascospores (11.5 to 25.3 × 4 to 7 μm). The pathogen was identified as Glomerella cingulata (Stoneman) Spauld. & Schrenk (anamorph Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. in Penz), based on morphological characteristics (1,2). Ten healthy, immature, attached fruits of common guava were inoculated with 3 × 106 conidia per ml of each of six isolates of G. cingulata, and ten were left untreated. Individual fruits were enclosed in plastic bags and kept at 15 to 20°C. After 72 h, bags were removed, and after 20 days, anthracnose symptoms were observed only on inoculated fruits. G. cingulata was reisolated from fruit lesions, and Koch's postulates were fulfilled. To our knowledge, this is the first report of G. cingulata on common guava in Argentina. References: (1) B. C. Sutton. The Coelomycetes. CMI, Kew, England, 1980. (2) J. A. von Arx. Phytopathol. Z. 29:413, 1957.