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Updated: Jul 17, 2026

Adaptation at the Extremes of Life: Experimental Evolution with the Extremophile Archaeon Sulfolobus acidocaldarius
Published on: June 14, 2024
Extreme size and sequence variation in the ITS rDNA of Bremia lactucae
Young-Joon Choi1, Seung-Boem Hong, Hyeon-Dong Shin
1Division of Environmental Science and Ecological Engineering, College of Life Sciences and Biotechnology, Korea University, Seoul, 136-701, Korea.
Abstract:
Bremia lactucae Regel (Chromista, Peronosporaceae) is an economically destructive pathogen, which causes downy mildew disease on lettuce (Lactuca sativa L.) worldwide. The ribosomal internal transcribed spacer (ITS) of Bremia lactucae isolates was analyzed for the first time. The ITS region of lettuce downy mildew was observed to have a size of 2458 bp; thereby, having one of the longest ITS sizes recorded to date. The majority of the extremely large sized ITS2 length of 2086 was attributed to the additional presences of nine repetitive elements with lengths of 179-194 bp, which between them shared the low homology of 48-69%. Comparison of the ITS2 sequences with the B. lactucae isolates from other host plants showed that isolates present on Lactuca sativa were distinct from those on L. indica var. laciniata, as well as Hemistepta and Youngia. We suggest the high degree of sequence heterogeneity exhibited in the ITS2 region of B. lactucae may warrant the specific detection and diagnosis of this destructive pathogen or its division into several distinct species.
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