Identification of cell wall-associated kinases as important regulators involved in Gossypium hirsutum resistance to Verticillium dahliae

Abstract

Background Verticillium wilt, caused by the soil borne fungus Verticillium dahliae, is a major threat to cotton production worldwide. An increasing number of findings indicate that WAK genes participate in plant−pathogen interactions, but their roles in cotton resistance to V. dahliae remain largely unclear. Results Here, we carried out a genome-wide analysis of WAK gene family in Gossypium hirsutum that resulted in the identification of 81 putative GhWAKs, which were all predicated to be localized on plasma membrane. In which, GhWAK77 as a representative was further located in tobacco epidermal cells using transient expression of fluorescent fusion proteins. All GhWAKs could be classified into seven groups according to their diverse protein domains, indicating that they might sense different outside signals to trigger intracellular signaling pathways that were response to various environmental stresses. A lot of cis-regulatory elements were predicted in the upstream region of GhWAKs and classified into four main groups including hormones, biotic, abiotic and light. As many as 28 GhWAKs, playing a potential role in the interaction between cotton and V. dahliae, were screened out by RNA-seq and qRT-PCR. To further study the function of GhWAKs in cotton resistance to V. dahliae, VIGS technology was used to silence GhWAKs. At 20 dpi, VIGSed plants exhibited more chlorosis and wilting than the control plants. The disease indices of VIGSed plants were also significantly higher than those of the control. Furthermore, silencing of GhWAKs significantly affected the expression of JA- and SA-related marker genes, increased the spread of V. dahliae in the cotton stems, dramatically compromised V. dahliae-induced accumulation of lignin, H2O2 and NO, but enhanced POD activity. Conclusion Our study presents a comprehensive analysis on cotton WAK gene family for the first time. Expression analysis and VIGS assay provided direct evidences on GhWAKs participation in the cotton resistance to V. dahliae.

A plant cell wall-associated kinase encoding gene is dramatically downregulated during nematode infection of potato

“…To better understand the relationship of the Soltu.DM.02G029720.1 encoded protein with other plant WAK/WAKL proteins, we performed a phylogenetic analysis that includes all the Arabidopsis and tomato WAK/WAKL proteins and several other plant WAK/WAKL proteins shown to have a role in plant resistance against pathogen infection. 7 , 10 , 14 The phylogenetic analysis revealed that the Soltu.DM.02G029720.1 encoded protein is clustered with SlWAKL2 and SlWAKL5 from tomato, GhWAK77 from cotton, AtWAKL14 and AtWAKL21 from Arabidopsis, and OsWAK25 and OsWAKL21.2 from rice ( Figure 1b ). The Soltu.DM.02G029720.1 protein showed the closest similarity to tomato SlWAKL2 (98% similarity), followed by GhWAK77 (73% similarity), SlWAKL5 (72% similarity), and OsWAK25 (68% similarity) and OsWAKL21.2 (55% similarity) from cotton, tomato, and rice, respectively.…”

“… 25 Plant WAK/WAKL protein sequences included are those encoded by the WAK / WAKL gene family from Arabidopsis and tomato, 5−6 as well as several other plant WAK / WAKL genes demonstrated to have a role in plant disease resistance. 7 , 10–15 …”

“… 2 Recently, genome-wide analysis and characterization of the WAK/WAKL gene family has been reported for many other plant species including tomato ( Solanum lycopersicum ) and cotton ( Gossypium hirsutum ). 6 , 7 …”

“…WAK/WAKL proteins have been increasingly recognized as important contributors to disease resistance against bacterial and fungal pathogens. 1 , 3 , 7–15 The Arabidopsis AtWAK1 is the best characterized WAK protein. AtWAK1 was shown to bind cell-wall-derived oligogalacturonides (OGs) and trigger OG-mediated defense responses effective against bacterial and fungal pathogens.…”

“… 3 WAK / WAKL genes involved in disease resistance have also been identified in other plant species including maize and cotton. 7 , 14 , 15 …”