Genes in the ERF family encode transcriptional regulators with a variety of functions involved in the developmental and physiological processes in plants. In this study, a comprehensive computational analysis identified 122 and 139 ERF family genes in Arabidopsis (Arabidopsis thaliana) and rice (Oryza sativa L. subsp. japonica), respectively. A complete overview of this gene family in Arabidopsis is presented, including the gene structures, phylogeny, chromosome locations, and conserved motifs. In addition, a comparative analysis between these genes in Arabidopsis and rice was performed. As a result of these analyses, the ERF families in Arabidopsis and rice were divided into 12 and 15 groups, respectively, and several of these groups were further divided into subgroups. Based on the observation that 11 of these groups were present in both Arabidopsis and rice, it was concluded that the major functional diversification within the ERF family predated the monocot/dicot divergence. In contrast, some groups/subgroups are species specific. We discuss the relationship between the structure and function of the ERF family proteins based on these results and published information. It was further concluded that the expansion of the ERF family in plants might have been due to chromosomal/segmental duplication and tandem duplication, as well as more ancient transposition and homing. These results will be useful for future functional analyses of the ERF family genes.

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Genome-Wide Analysis of the ERF Gene Family in Arabidopsis and Rice

Despite its simple two-carbon structure, the olefin ethylene is a potent modulator of plant growth and development ([Ecker, 1995][1]). The plant hormone ethylene is involved in many aspects of the plant life cycle, including seed germination, root hair development, root nodulation, flower senescence

Ethylene biosynthesis and signaling networks.

Transcription factors in plant defense and stress responses.

■ Abstract Many disease resistance (R) proteins of plants detect the presence of disease-causing bacteria, viruses, or fungi by recognizing specific pathogen effector molecules that are produced during the infection process. Effectors are often pathogen proteins that probably evolved to subvert various host processes for promotion of the pathogen life cycle. Five classes of effector-specific R proteins are known, and their sequences suggest roles in both effector recognition and signal transduction. Although some R proteins may act as primary receptors of pathogen effector proteins, most appear to play indirect roles in this process. The functions of various R proteins require phosphorylation, protein degradation, or specific localization within the host cell. Some signaling components are shared by many R gene pathways whereas others appear to be pathway specific. New technologies arising from the genomics and proteomics revolution will greatly expand our ability to investigate the role of R proteins in plant disease resistance.

Understanding the functions of plant disease resistance proteins.

Elucidating the mechanisms involved in ripening of climacteric fruit and the role that ethylene plays in the process are key to understanding fruit production and quality. In this review, which is based largely on research in tomato, particular attention is paid to the role of specific isoforms of ACC synthase and ACC oxidase in controlling ethylene synthesis during the initiation and subsequent autocatalytic phase of ethylene production during ripening. Recent information on the structure and role of six different putative ethylene receptors in tomato is discussed, including evidence supporting the receptor inhibition model for ripening, possible differences in histidine kinase activity between receptors, and the importance of receptor LeETR4 in ripening. A number of ethylene-regulated ripening-related genes are discussed, including those involved in ethylene synthesis, fruit texture, and aroma volatile production, as well as experiments designed to elucidate the ethylene signalling pathway from receptor through intermediate components similar to those found in Arabidopsis, leading to transcription factors predicted to control the expression of ethylene-regulated genes.

Ethylene biosynthesis and action in tomato: a model for climacteric fruit ripening

The Pti4, Pti5, and Pti6 proteins from tomato were identified based on their interaction with the product of the Pto disease resistance gene, a Ser-Thr protein kinase. They belong to the ethylene-response factor (ERF) family of plantunique transcription factors and bind specifically to the GCC-box cis element present in the promoters of many pathogenesis-related ( PR ) genes. Here, we show that these tomato ERFs are localized to the nucleus and function in vivo as transcription activators that regulate the expression of GCC box‐containing PR genes. Expression of Pti4 , Pti5 , or Pti 6 in Arabidopsis activated the expression of the salicylic acid‐regulated genes PR1 and PR2 . Expression of jasmonic acid‐ and ethylene-regulated genes, such as PR3 , PR4 , PDF1.2 , and Thi2.1 , was affected differently by each of the three tomato ERFs, with Arabidopsis -Pti4 plants having very high levels of PDF1.2 transcripts. Exogenous application of salicylic acid to Arabidopsis- Pti4 plants suppressed the increased expression of PDF1.2 but further stimulated PR1 expression. Arabidopsis plants expressing Pti4 displayed increased resistance to the fungal pathogen Erysiphe orontii and increased tolerance to the bacterial pathogen Pseudomonas syringae pv tomato . These results indicate that Pti4, Pti5, and Pti6 activate the expression of a wide array of PR genes and play important and distinct roles in plant defense.

/pdf/tomato-transcription-factors-pti4-pti5-and-pti6-activate-3xgegmazxs.pdf

Tomato Transcription Factors Pti4, Pti5, and Pti6 Activate Defense Responses When Expressed in Arabidopsis

The tomato Pti4 gene encodes a transcription factor that was identified on the basis of its specific interaction with the product of the Pto disease resistance gene in a yeast two-hybrid system. We show here that the Pti4 protein specifically binds the GCC-box cis element, which is present in the promoter region of many pathogenesis-related (PR) genes. Expression of the Pti4 gene in tomato leaves was rapidly induced by ethylene and by infection with Pseudomonas syringae pv tomato, and this induction preceded expression of GCC-box-containing PR genes. Although salicylic acid also induced Pti4 gene expression, it did not induce GCC-box PR genes. Rather, salicylic acid antagonized ethylene-mediated expression of GCC-box PR genes. We demonstrate that the Pti4 protein is specifically phosphorylated by the Pto kinase and that this phosphorylation enhances binding of Pti4 to the GCC box. In addition, induced overexpression of Pto and Pti4 in tomato leaves resulted in a concomitant increase in GCC-box PR genes. Our results support a model in which phosphorylation of the Pti4 protein by the Pto kinase enhances the ability of Pti4 to activate expression of GCC-box PR genes in tomato.

/pdf/pti4-is-induced-by-ethylene-and-salicylic-acid-and-its-45snlefqvb.pdf

Pti4 Is Induced by Ethylene and Salicylic Acid, and Its Product Is Phosphorylated by the Pto Kinase

The central importance of protein phosphorylation in plant defense responses has been demonstrated by the isolation of several disease-resistance genes that encode protein kinases In addition, there are many reports of changes in protein phosphorylation accompanying plant responses to pathogens In contrast, little is known about the role of protein dephosphorylation in regulating plant defenses We report that expression of the LePP2Ac1 gene, which encodes a catalytic subunit of the heterotrimeric protein phosphatase 2A (PP2Ac), is rapidly induced in resistant tomato leaves upon inoculation with an avirulent strain of Pseudomonas syringae pv tomato By analysis of PP2Ac gene sequences from several plant species, we found that PP2Ac genes cluster into two subfamilies, with LePP2Ac1 belonging to subfamily I Virus-induced gene silencing (VIGS) in Nicotiana benthamiana was used to suppress expression of genes from subfamily I and not from subfamily II The PP2Ac-silenced plants had greatly decreased PP2A activity, constitutively expressed pathogenesis-related (PR) genes, and developed localized cell death in stems and leaves In addition, the plants were more resistant to a virulent strain of P syringae pv tabaci and showed an accelerated hypersensitive response (HR) to effector proteins from both P syringae and the fungal pathogen, Cladosporium fulvum Thus, catalytic subunits of PP2Ac subfamily I act as negative regulators of plant defense responses likely by de-sensitizing protein phosphorylation cascades

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-313X.2004.02073.x

Yong-Qiang Gu

Papers

Tomato Transcription Factors Pti4, Pti5, and Pti6 Activate Defense Responses When Expressed in Arabidopsis

Pti4 Is Induced by Ethylene and Salicylic Acid, and Its Product Is Phosphorylated by the Pto Kinase

Silencing of subfamily I of protein phosphatase 2A catalytic subunits results in activation of plant defense responses and localized cell death.