Decomposition of dynamic transcriptomic responses during effector-triggered immunity reveals conserved responses in two distinct plant cell populations

Rapid plant immune responses in the appropriate cells are needed for effective defense against pathogens.Although transcriptome analysis is often used to describe overall immune responses,collection of transcriptome data with sufficient resolution in both space and time is challenging.We reanalyzed public Arabidopsis time-course transcriptome data obtained after low-dose inoculation with a Pseudomonas syringae strain expressing the effector AvrRpt2,which induces effector-triggered immunity in Arabidopsis.Double-peak time-course patterns are prevalent among thousands of upregulated genes.We implemented a multicompartment modeling approach to decompose the double-peak pattern into two single-peak patterns for each gene.The decomposed peaks reveal an“echoing”pattern:the peak times of the first and second peaks correlate well across most upregulated genes.We demonstrated that the two peaks likely represent responses of two distinct cell populations that respond either cell autonomously or indirectly to AvrRpt2.Thus,the peak decomposition has extracted spatial information from the time-course data.The echoing pattern also indicates a conserved transcriptome response with different initiation times between the two cell populations despite different elicitor types.A gene set highly overlapping with the conserved gene set is also upregulated with similar kinetics during pattern-triggered immunity.Activation of a WRKY network via different entry-point WRKYs can explain the similar but not identical transcriptome responses elicited by different elicitor types.We discuss potential benefits of the properties of the WRKY activation network as an immune signaling network in light of pressure from rapidly evolving pathogens.

Eureka lemon zinc finger protein ClDOF3.4 interacts with citrus yellow vein clearing virus coat protein to inhibit viral infection

Citrus yellow vein clearing virus(CYVCV)is a new citrus virus that has become an important factor restricting the development of China’s citrus industry,and the CYVCV coat protein(CP)is associated with viral pathogenicity.In this study,the Eureka lemon zinc finger protein(ZFP)ClDOF3.4 was shown to interact with CYVCV CP in vivo and in vitro.Transient expression of ClDOF3.4 in Eureka lemon induced the expression of salicylic acid(SA)-related and hypersensitive response marker genes,and triggered a reactive oxygen species burst,ion leakage necrosis,and the accumulation of free SA.Furthermore,the CYVCV titer in ClDOF3.4 transgenic Eureka lemon plants was approximately 69.4%that in control plants 6 mon after inoculation,with only mild leaf chlorotic spots observed in those transgenic plants.Taken together,the results indicate that ClDOF3.4 not only interacts with CP but also induces an immune response in Eureka lemon by inducing the SA pathways.This is the first report that ZFP is involved in the immune response of a citrus viral disease,which provides a basis for further study of the molecular mechanism of CYVCV infection.

Innate Immunity of Phlomis purpurea against Phytophthora cinnamomi: A Transcriptomic Analysis

Phlomis purpurea L.grows spontaneously in dry and stony habitats from the south of Iberian Peninsula and in cork oak(Quercus suber L.)and holm oak(Q.ilex ssp.rotundifolia,Lam.)plantations infested with Phytophthora cinnamomi(Rands).The aim of this study is to understand the genetic basis of P.purpurea innate immunity to this pathogen.The transcriptome analysis of P.purpurea upon challenging with P.cinnamomi revealed a set of up-regulated genes,related to signaling,transcription factors and response to stress.Transcripts involved in the synthesis of a number of proteins,namely:ANKYRIN,AP2,AQUAPORIN,ARMADILLO,At1G69870-LIKE,BHLH,BON1,CALMODULIN,CALNEXIN,CALRETICULINE,CC-NBS-LRR,CHAPERONE,CYTOCHROME,DUF,GH3,GMP,G-TYPE,LIPOXYGENASE,MLO-LIKE,MYB,NAC,NBS-LRR,PENTATRICOPEPTIDE,SUBTILISIN,WAK,bZIP and hormones such as BRASSINOSTEROID,JASMONATE,SALICYLATE,ETHYLENE-RESPONSIVE were identified.P.purpurea ability to cope with P.cinnamomi attack is based on the expression of a set of transcription factors and signaling molecules targeted by the pathogen.The information gathered contributes to the elucidation of the overall response of P.purpurea to P.cinnamomi attempted infection which can be helpful for improving woody species resistance to pathogenic oomycetes.