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Alternaria alternata (A. alternata) is a common pathogen that greatly influences apples' quantity and quality. However, chemical treatments produce increased health risks along with decreased food and environmental safety. Advancements in plant molecular biology, such as transgenic technology, have increased apple trees' resistance to pathogens and have therefore attracted widespread attention. WRKY transcription factors are involved in abiotic and biotic stress regulation; however, their biological role in non-model plants such as apple, is still unknown. In this investigation, MdWRKY120 was isolated from the 'GL-3′ apple to determine its function during Alternaria alternate infection. The MdWRKY120-GFP fusion protein was located in the nucleus. MdWRKY120 in yeast cells exhibited activating transcriptional activity, meaning it is a transcription activator. MdWRKY120 overexpression transgenic plants were more sensitive to A. alternata, while RNAi transgenic plants showed increased resistance to A. alternata. This investigation demonstrates that MdWRKY120 enhances the susceptibility of apples to A. alternata. [ABSTRACT FROM AUTHOR]

Summary: To expand the cultivation area of apple (Malus×domestica Borkh.) and select resistant varieties by genetic engineering, it is necessary to clarify the mechanism of salt and osmotic stress tolerance in apple. The MdMYB46 transcription factor was identified, and the stress treatment test of MdMYB46‐overexpressing and MdMYB46‐RNAi apple lines indicated that MdMYB46 could enhance the salt and osmotic stress tolerance in apple. In transgenic Arabidopsis and apple, MdMYB46 promoted the biosynthesis of secondary cell wall and deposition of lignin by directly binding to the promoter of lignin biosynthesis‐related genes. To explore whether MdMYB46 could coordinate stress signal transduction pathways to cooperate with the formation of secondary walls to enhance the stress tolerance of plants, MdABRE1A, MdDREB2A and dehydration‐responsive genes MdRD22 and MdRD29A were screened out for their positive correlation with osmotic stress, salt stress and the transcriptional level of MdMYB46. The further verification test demonstrated that MdMYB46 could activate their transcription by directly binding to the promoters of these genes. The above results indicate that MdMYB46 could enhance the salt and osmotic stress tolerance in apple not only by activating secondary cell wall biosynthesis pathways, but also by directly activating stress‐responsive signals. [ABSTRACT FROM AUTHOR]

Apple trees encounter problems such as stressful environments and pathogen infection throughout their entire growth and development, which limits apple production. WRKY transcription factors play a vital role in the defense against pathogens, but their functions in apple trees need to be further explored. In this study, the MdWRKY61 gene, which encodes the WRKY61 protein of the WRKY group II family, was isolated from GL-3 apple. Tobacco subcellular localization experiments showed that the MdWRKY61 protein is located in the nucleus. Quantitative reverse transcription PCR analysis suggested that MdWRKY61 is highly expressed in the roots and fruits of apples and is rapidly induced in response to salicylic acid, jasmonic acid and Colletotrichum siamense. We obtained MdWRKY61 overexpression lines through Agrobacterium -mediated stable genetic transformation of apple. Subsequent experiments revealed that overexpression of MdWRKY61 increased the resistance of apple to Colletotrichum siamense and promoted the upregulation of defense-related gene expression. Taken together, our data provide insights that MdWRKY61 plays an important role in apple resistance to fungal disease. • First research on the function of MdWRKY61. • MdWRKY61 was induced by Colletotrichum siamense , SA and JA. • MdWRKY61 can improve the resistance of apples to Colletotrichum siamense. [ABSTRACT FROM AUTHOR]