Abstract
Plant-parasitic nematodes are destructive plant pathogens that cause significant yield losses. They induce highly specialized feeding sites (NFS) in infected plant roots from which they withdraw nutrients. In order to establish these NFS, it is thought that the nematodes manipulate the molecular and physiological pathways of their hosts. Evidence is accumulating that the plant signalling molecule auxin is involved in the initiation and development of the feeding sites of sedentary plant-parasitic nematodes. Intercellular transport of auxin is essential for various aspects of plant growth and development. Here, we analysed the spatial and temporal expression of PIN auxin transporters during the early events of NFS establishment using promoter-GUS/GFP fusion lines. Additionally, single and double pin mutants were used in infection studies to analyse the role of the different PIN proteins during cyst nematode infection. Based on our results, we postulate a model in which PIN1-mediated auxin transport is needed to deliver auxin to the initial syncytial cell, whereas PIN3 and PIN4 distribute the accumulated auxin laterally and are involved in the radial expansion of the NFS. Our data demonstrate that cyst nematodes are able to hijack the auxin distribution network in order to facilitate the infection process.
Highlights
Plant-parasitic nematodes are major agricultural pests world-wide and are responsible for global agricultural losses amounting to an estimated $157 billion annually [1]
The auxin-insensitive tomato mutant dgt was shown to be de facto resistant to cyst nematodes, while in the model plant Arabidopsis thaliana a significant reduction in the number of developing cyst nematodes was observed in the axr2/iaa7 mutant that is defective in auxin signalling [10]
Intercellular transport of auxin is essential for various aspects of plant growth and development and it was shown that it accumulates during the early stages of nematode infection
Summary
Plant-parasitic nematodes are major agricultural pests world-wide and are responsible for global agricultural losses amounting to an estimated $157 billion annually [1]. Most of the damage is causes by sedentary plant-parasitic nematodes of the family Heteroderidae which transform differentiated plant root cells into nematode feeding sites (NFS). Cyst nematodes such as Heterodera schachtii induce syncytia by cell wall dissolution and subsequent fusion of the infected cell with its neighbouring cells. More recently in Arabidopsis, the upregulation of the auxin responsive DR5 reporter could be demonstrated shortly after nematode infection [11,12] This local auxin accumulation could be due to auxin directly secreted by the nematode [13] or could be a result of directional auxin transport towards the feeding site initial. Application of the synthetic auxin transport inhibitor NPA hampers the expansion of syncytia resulting in a reduction of nematode development [10]
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