AUTHOR=Liu Bin , Liu Xingwang , Liu Ying , Xue Shudan , Cai Yanling , Yang Sen , Dong Mingming , Zhang Yaqi , Liu Huiling , Zhao Binyu , Qi Changhong , Zhu Ning , Ren Huazhong 

TITLE=The Infection of Cucumber (Cucumis sativus L.) Roots by Meloidogyne incognita Alters the Expression of Actin-Depolymerizing Factor (ADF) Genes, Particularly in Association with Giant Cell Formation

JOURNAL=Frontiers in Plant Science

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2016.01393

DOI=10.3389/fpls.2016.01393

ISSN=1664-462X

ABSTRACT=<p>Cucumber (<italic>Cucumis sativus</italic> L.) is threatened by substantial yield losses due to the south root-knot nematode (<italic>Meloidogyne incognita</italic>). However, understanding of the molecular mechanisms underlying the process of nematode infection is still limited. In this study, we found that <italic>M. incognita</italic> infection affected the structure of cells in cucumber roots and treatment of the cytoskeleton inhibitor (cytochalasin D) reduced root-knot nematode (RKN) parasitism. It is known that Actin-Depolymerizing Factor (ADF) affects cell structure, as well as the organization of the cytoskeleton. To address the hypothesis that nematode-induced abnormal cell structures and cytoskeletal rearrangements might be mediated by the <italic>ADF</italic> genes, we identified and characterized eight cucumber <italic>ADF</italic> (<italic>CsADF</italic>) genes. Phylogenetic analysis showed that the cucumber <italic>ADF</italic> gene family is grouped into four ancient subclasses. Expression analysis revealed that <italic>CsADF1, CsADF2-1, CsADF2-2, CsADF2-3</italic> (Subclass I), and <italic>CsADF6</italic> (Subclass III) have higher transcript levels than <italic>CsADF7-1, CsADF7-2</italic> (Subclass II genes), and <italic>CsADF5</italic> (Subclass IV) in roots. Members of subclass I genes (<italic>CsADF1, CsADF2-1, CsADF2-2</italic>, and <italic>CsADF2-3</italic>), with the exception of <italic>CsADF2-1</italic>, exhibited a induction of expression in roots 14 days after their inoculation (DAI) with nematodes. However, the expression of subclass II genes (<italic>CsADF7-1</italic> and <italic>CsADF7-2</italic>) showed no significant change after inoculation. The transcript levels of <italic>CsADF6</italic> (Subclass III) showed a specific induction at 21 DAI, while <italic>CsADF5</italic> (Subclass IV) was weakly expressed in roots, but was strongly up-regulated as early as 7 DAI. In addition, treatment of roots with cytochalasin D caused an approximately 2-fold down-regulation of the <italic>CsADF</italic> genes in the treated plants. These results suggest that <italic>CsADF</italic> gene mediated actin dynamics are associated with structural changes in roots as a consequence of <italic>M. incognita</italic> infection.</p>