Parasitic plants have a unique heterotrophic lifestyle based on the extraction of water and nutrients from host plants. Some parasitic plant species, particularly those of the family Orobanchaceae, attack crops and cause substantial yield losses. The breeding of resistant crop varieties is an inexpensive way to control parasitic weeds, but often does not provide a long-lasting solution because the parasites rapidly evolve to overcome resistance. Understanding mechanisms underlying naturally occurring parasitic plant resistance is of great interest and could help to develop methods to control parasitic plants. In this review, we describe the virulence mechanisms of parasitic plants and resistance mechanisms in their hosts, focusing on obligate root parasites of the genera Orobanche and Striga. We noticed that the resistance (R) genes in the host genome often encode proteins with nucleotide-binding and leucine-rich repeat domains (NLR proteins), hence we proposed a mechanism by which host plants use NLR proteins to activate downstream resistance gene expression. We speculated how parasitic plants and their hosts co-evolved and discussed what drives the evolution of virulence effectors in parasitic plants by considering concepts from similar studies of plant–microbe interaction. Most previous studies have focused on the host rather than the parasite, so we also provided an updated summary of genomic resources for parasitic plants and parasitic genes for further research to test our hypotheses. Finally, we discussed new approaches such as CRISPR/Cas9-mediated genome editing and RNAi silencing that can provide deeper insight into the intriguing life cycle of parasitic plants and could potentially contribute to the development of novel strategies for controlling parasitic weeds, thereby enhancing crop productivity and food security globally.

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Abstract Background: WRKY transcription factors play important roles in various physiological processes and stress responses in flowering plants. However, the information about WRKY genes in Helianthus annuus L. (common sunflower) is limited. Results: Ninety WRKY (HaWRKY) genes were identified and renamed according to their locations on chromosomes. Further phylogenetic analyses classified them into four main groups including a species-specific WKKY group and HaWRKY genes within same group or subgroup generally showed similar exon-intron structures and motif compositions. The tandem and segmental duplication possibly contributed to the diversity and expansion of HaWRKY gene families. Synteny analyses of sunflower WRKY genes provided deep insight to the evolution of HaWRKY genes. Transcriptomic and qRT-PCR analyses of HaWRKY genes displayed distinct expression patterns in different plant tissues, as well as under various abiotic and biotic stresses. Conclusions: Ninety WRKY (HaWRKY) genes were identified from H. annuus L. and classified into four groups. Structures of HaWRKY proteins and their evolutionary characteristics were also investigated. The characterization of HaWRKY genes and their expression profiles under biotic and abiotic stresses in this study provide a foundation for further functional analyses of these genes. Therefore, these functional genes related to increasing the plant tolerance or improving the crop quality, could be applied for the crop improvement..

Background: WRKY transcription factors play important roles in various physiological processes and stress responses in flowering plants. However, the information about WRKY genes in Helianthus annuus L. (common sunflower) is limited. Results: Ninety WRKY (HaWRKY) genes were identified and renamed according to their locations on chromosomes. Further phylogenetic analyses classified them into four main groups including a species-specific WKKY group and HaWRKY genes within same group or subgroup generally showed similar exon-intron structures and motif compositions. The tandem and segmental duplication possibly contributed to the diversity and expansion of HaWRKY gene families. Synteny analyses of sunflower WRKY genes provided deep insight to the evolution of HaWRKY genes. Transcriptomic and qRT-PCR analyses of HaWRKY genes displayed distinct expression patterns in different plant tissues, as well as under various abiotic and biotic stresses. Conclusions: Ninety WRKY (HaWRKY) genes were identified from H. annuus L. and classified into four groups. Structures of HaWRKY proteins and their evolutionary characteristics were also investigated. The characterization of HaWRKY genes and their expression profiles under biotic and abiotic stresses in this study provide a foundation for further functional analyses of these genes and will be beneficial to crop improvement.