Abstract
The EXO70 gene family is involved in different biological processes in plants, ranging from plant polar growth to plant immunity. To date, analysis of the EXO70 gene family has been limited in Triticeae species, e.g., hexaploidy Triticum aestivum and its ancestral/related species. By in silico analysis of multiple Triticeae sequence databases, a total of 200 EXO70 members were identified. By homologue cloning approaches, 15 full-length cDNA of EXO70s were cloned from diploid Haynaldia villosa. Phylogenetic relationship analysis of 215 EXO70 members classified them into three groups (EXO70.1, EXO70.2, and EXO70.3) and nine subgroups (EXO70A to EXO70I). The distribution of most EXO70 genes among different species/sub-genomes were collinear, implying their orthologous relationship. The EXO70A subgroup has the most introns (at least five introns), while the remaining seven subgroups have only one intron on average. The expression profiling of EXO70 genes from wheat revealed that 40 wheat EXO70 genes were expressed in at least one tissue (leaf, stem, or root), of which 25 wheat EXO70 genes were in response to at least one biotic stress (stripe rust or powdery mildew) or abiotic stress (drought or heat). Subcellular localization analysis showed that ten EXO70-V proteins had distinct plasma membrane localization, EXO70I1-V showed a distinctive spotted pattern on the membrane. The 15 EXO70-V genes were differentially expressed in three tissue. Apart from EXO70D2-V, the remaining EXO70-V genes were in response to at least one stress (flg22, chitin, powdery mildew, drought, NaCl, heat, or cold) or phytohormones (salicylic acid, methyl jasmonate, ethephon, or abscisic acid) and hydrogen peroxide treatments. This research provides a genome-wide glimpse of the Triticeae EXO70 gene family and those up- or downregulated genes require further validation of their biological roles in response to biotic/abiotic stresses.
Highlights
The exocyst complex is an evolutionarily conserved octameric tethering factor, which mediates the fusion of post-Golgi secretory vesicle with the plasma membrane (PM) and plays a major role in exocytosis [1,2]
We only identified 15 EXO70s in diploid H. villosa, which is much less than the average number for other diploid species
We found that the EXO70C2 is on the 4BS of common wheat and T. dicoccoides (Figure 3a,b), on the 4DS of common wheat and Ae. tauschii (Figure 3a,d), but on the 4AL of common wheat and T. dicoccoides (Figure 3a,b)
Summary
The exocyst complex is an evolutionarily conserved octameric tethering factor, which mediates the fusion of post-Golgi secretory vesicle with the plasma membrane (PM) and plays a major role in exocytosis [1,2]. Evidence has accumulated for the critical role of EXO70s in plant-pathogen interactions or responses to abiotic stresses. Three of the 23 members of the Arabidopsis EXO70 gene family (EXO70B1, EXO70B2 and EXO70H1) have been proven to be involved in plant immunity [26]. The importance of EXO70 in plant immunity was shown by the fact that some of the EXO70s were targets of the secreted effectors of the plant pathogen Both OsEXO70F2 and OsEXO70F3 were targets of the Magnaporthe oryzae effector AVR-Pii, and OsEXO70F3 was proven to play an important role in Pii-dependent resistance by interacting with AVR-Pii [35]. The obta2i.nRedesruelstuslts would help us to understand the evolution and diversification of the EXO70s among Triticeae species and their potential roles in plant immunity and responses to abiotic stresses. Tachieds11wiedreenitnicdailcaamtedinionarceiddsfrwameree.iTndheictahteredeincorleodrsfroafmbela.cTkh,ered and tbhlrueee rceoplorersseonftbtlhaeckl,erveedl oanf dsimbluilearrietyproefseanmt itnhoe alecvidels,offrsoimmihlairgihtytooflaomwi.n(ob)acSiedqsu, fernocme shiimghilatority analyloswis.u(sbin) gSethque eRnpcerosgirmamilamriitnygalnaanlgyusaisgue.sTinhgetchoeloRr spcraolegrbaamr rmepinregselanntsguseaqguee. nTcheesicmoliolarrsitcyalbeetbwareen differreepnrtegseenntess.sReqedueanncde yseimlloilwariintydibcaettwe teheant tdhieffseereqnutengceenseism. iRlaerdityanwdasygelrleoawterinthdaicna8te0%thaant dth6e0%, respseecqtiuveenlyc.eBlsuime iinladriictyatewsatshagtrtehaetesreqtuheannce80si%mialanrdity6w0%as, lreesssptehcatinv4el0y%. .Blue indicates that the sequence similarity was less than 40%
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