Pine wilt disease causes cavitation around the resin canals and irrecoverable xylem conduit dysfunction

Irreversible xylem dysfunction is triggered by patchy cavitation of tracheids around the resin canals by pine wood nematodes. Abstract Physiological mechanisms of irreversible hydraulic dysfunction in seedlings infected with pine wilt disease (PWD) are still unclear. We employed cryo-scanning electr...

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Published in:Journal of experimental botany 2018-01, Vol.69 (3), p.589-602
Main Authors: Yazaki, Kenichi, Takanashi, Takuma, Kanzaki, Natsumi, Komatsu, Masabumi, Levia, Delphis F, Kabeya, Daisuke, Tobita, Hiroyuki, Kitao, Mitsutoshi, Ishida, Atsushi
Format: Article
Language:English
Subjects:
Animals
Droughts
Pinus - parasitology
Pinus - physiology
Plant Diseases - parasitology
Tylenchida - physiology
Xylem - parasitology
Xylem - physiology
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Summary:Irreversible xylem dysfunction is triggered by patchy cavitation of tracheids around the resin canals by pine wood nematodes. Abstract Physiological mechanisms of irreversible hydraulic dysfunction in seedlings infected with pine wilt disease (PWD) are still unclear. We employed cryo-scanning electron microscopy (cryo-SEM) to investigate the temporal and spatial changes in water distribution within the xylem of the main stem of 2-year-old Japanese black pine seedlings infested by pine wood nematodes (PWNs). Our experiment was specifically designed to compare the water relations among seedlings subjected to the following water treatment and PWN combinations: (i) well-watered versus prolonged drought (no PWNs); and (ii) well-watered with PWNs versus water-stressed with PWNs (four treatments in total). Cryo-SEM imaging observations chronicled the development of patchy cavitations in the xylem tracheids of the seedlings influenced by PWD. With the progression of drought, many pit membranes of bordered pits in the xylem of the main stem were aspirated with the decrease in water potential without xylem cavitation, indicating that hydraulic segmentation may exist between tracheids. This is the first study to demonstrate conclusively that explosive and irreversible cavitations occurred around the hydraulically vulnerable resin canals with the progression of PWD. Our findings provide a more comprehensive understanding of stressors on plant-water relations that may eventually better protect trees from PWD and assist with the breeding of trees more tolerant to PWD.
ISSN:0022-0957
1460-2431
DOI:10.1093/jxb/erx417