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Aoxue Wang, Fanjuan Meng, Xiangyang Xu, Yong Wang and Jingfu Li

Leaf mold, caused by the fungus Cladosporium fulvum, is a serious disease of tomato. In the current study, the main physiological races of C. fulvum collected from three northeastern provinces of China were identified using a set of identification hosts. The results showed that the prevalent pathogenic physiological races were 1.2.3, 1.3, 3,, and 1.2.4. F1, F2, and BC1 tomato plants were obtained by crossing C. fulvum-resistant cultivar 03748 carrying the Cf-6 gene and susceptible cultivar 03036. Three 10-mer oligonucleotide random amplified polymorphic DNA (RAPD) primers and two simple sequence repeat (SSR) primers were selected for the further molecular marking analysis after 210 RAPD primers and 50 SSR primers were screened using the bulked segregate analysis method. The polymorphic DNA bands were amplified among parents, 10 F1 plants, 184 F2 plants including 145 resistant plants and 39 sensitive plants using three RAPD primers and two SSR primers so that three RAPD molecular markers and two SSR molecular markers linked to the Cf-6 loci were identified. Three RAPD markers were linked to the Cf-6 resistant locus separated with 8.7 cM, 20.3 cM, and 33.4 cM. Also, one RAPD codominant marker S374619/559 was found. The locations of the two SSR markers were 12.6 cM and 9.7 cM away from the Cf-6 locus. After cloning and sequencing two specific DNA fragments closely connected to the Cf-6 resistant and susceptible alleles respectively, in the RAPD codominant marker S374619/559 and one codominant sequence characterized amplified region marker S674619/559 was converted from RAPD marker S374619/559. In the RAPD marker S374619/559, the length difference of two specific fragments, 619-bp fragment and 559-bp fragment, is the result of one insertion (60 bp) in the 619-bp fragment. These markers will facilitate the selection of resistant tomato germplasm containing the Cf-6 gene and cloning of Cf-6 to breed new C. fulvum resistant tomato cultivars.

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Jingkang Hu, Yingmei Gao, Tingting Zhao, Jingfu Li, Meini Yao and Xiangyang Xu

Members of the zinc-finger homeodomain (ZF-HD) family play a key role in the control of plant growth and development, which are involved in plant responses to stress. Although many functional studies of this gene family have been performed in different plants, the features of this family in tomato (Solanum lycopersicum) remain unknown. In this study, we identified 22 ZF-HD genes in the tomato genome and classified them into seven groups located on six chromosomes. Expression of 15 ZF-HD genes in tomato was studied in different tissues to identify their putative functions in many aspects of plant growth and development. Based on previous phylogenetic analyses in arabidopsis (Arabidopsis thaliana), our results showed that some tomato SL-ZH (S. lycopersicum zinc-finger homeodomain) genes cluster into the same neighbor-joining (NJ) branch as arabidopsis, indicating that these genes may share similar structures and functions in these plants. Gene expression analysis demonstrated that the tomato ZF-HD gene may be involved in abiotic stress responses, the SL-ZH13 gene in cold stress and the SL-ZH15 gene in drought stress; almost all tomato ZF-HD genes were responsive to salt stress, except for SL-ZH7, -ZH8, and -ZH22. However, the structures and functions of unknown groups require further research. In conclusion, this study identified tomato ZF-HD genes and analyzed their gene structures, subfamily distribution, and expression characteristics. These experiments combined with previous research findings reveal significant information and insight for future studies on the agronomic features and stress resistance in tomato.

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Yingmei Gao, Jingkang Hu, Tingting Zhao, Xiangyang Xu, Jingbin Jiang and Jingfu Li

BRI1-EMS-suppressor 1 (BES1) is a transcription factor (TF) that functions as a master regulator of brassinosteroid (BR)-regulated gene expression. Here, we provide a complete overview of Solanum lycopersicum BES1 (SLB) genes, including phylogeny, gene structure, protein motifs, chromosome locations and expression characteristics. Through bioinformatic analysis, we compared the sequences of SLB genes, arabidopsis (Arabidopsis thaliana) genes, and chinese cabbage (Brassica pekinensis) genes. All of the gene sequences were divided into three groups by cluster analysis. SLB genes were mapped to the eight tomato (S. lycopersicum) chromosomes. Bioinformatic analysis showed that SLB genes shares similarities with the proteins from other plants, though different species exhibit specific features. The expression patterns of SLB genes in various tissues and under different abiotic conditions were analyzed by quantitative reverse transcription polymerase chain reaction. SLB genes were found to be induced by multiple stresses, particularly salt stress, indicating that SLB genes may have important roles in the response to unfavorable environmental changes. This study provides insight into the evolution of SLB genes and may aid in the further functional identification of BES1 proteins and the response of tomato plants to different stresses.

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Tingting Zhao, Jingkang Hu, Yingmei Gao, Ziyu Wang, Yufang Bao, Xiaochun Zhang, Huanhuan Yang, Dongye Zhang, Jingbin Jiang, He Zhang, Jingfu Li, Qingshan Chen and Xiangyang Xu

Zinc finger-homeodomains (ZF-HDs) are considered transcription factors that are involved in a variety of life activities in plants, but their function in regulating plant salt stress tolerance is unclear. The SL-ZH13 gene is significantly upregulated under salt stress treatment in tomato (Solanum lycopersicum) leaves, per our previous study. In this study, to further understand the role that the SL-ZH13 gene played in the response process of tomato plants under salt stress, the virus-induced gene silencing (VIGS) method was applied to down-regulate SL-ZH13 expression in tomato plants, and these plants were treated with salt stress to analyze the changes in salt tolerance. The silencing efficiency of SL-ZH13 was confirmed by quantitative real-time PCR analysis. SL-ZH13-silenced plants wilted faster and sooner than control plants under the same salt stress treatment condition, and the main stem bending angle of SL-ZH13-silenced plants was smaller than that of control plants. Physiological analysis showed that the activities of superoxide dismutase, peroxidase, and proline content in SL-ZH13-silenced plants were lower than those in control plants at 1.5 and 3 hours after salt stress treatment. The malondialdehyde content of SL-ZH13-silenced plants was higher than that in control plants at 1.5 and 3 hours after salt stress treatment; H2O2 and O2 - accumulated much more in leaves of SL-ZH13-silenced plants than in leaves of control plants. These results suggested that silencing of the SL-ZH13 gene affected the response of tomato plants to salt stress and decreased the salt stress tolerance of tomato plants.