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.

Clarifying the stress signal transduction pathway would be helpful for understanding the abiotic stress resistance mechanism in apple (Malus × domestica Borkh.) and could assist in the development of new varieties with high stress tolerance by genetic engineering. The key NAC transcription factor SND1, which is involved in the lignin biosynthesis process in apple, was functionally analyzed. The results of the stress treatments indicated that MdSND1 could be induced by salt, mannitol and ABA. Compared with wild-type GL-3 plants, MdSND1-overexpressing apple plants with greater antioxidant capacity and lignin were more resistant to salt and simulated osmotic stress, while RNAi plants were more vulnerable. Additionally, molecular experiments confirmed that MdSND1 could regulate the biosynthesis of lignin by activating the transcription of MdMYB46/83. Moreover, genes known to be involved in the stress signal transduction pathway (MdAREB1A, MdAREB1B, MdDREB2A, MdRD29A, and MdRD22) were screened for their close correlations with the expression of MdSND1 and the response to salt and osmotic stress. Multiple verification tests further demonstrated that MdSND1 could directly bind to these gene promoters and activate their transcription. The above results revealed that MdSND1 is directly involved in the regulation of lignin biosynthesis and the signal transduction pathway involved in the response to both salt and osmotic stress in apple.

To investigate the nutritional characteristics of purple wheat, 41 kinds of nutrients were measured in seven purple wheat lines using one white wheat variety as control sample. Correlation analysis of nutrient contents was performed. Results show that the amounts of 40 kinds of nutrients in the purple wheat lines are higher than those of the control. For example, the amounts of sodium (Na) and manganese (Mn) in purple wheat are higher than the standards by 311.77-2017.65% and 548.15-733.33%, respectively; the contents of b + g-vitamin E is higher than the standards by 300%; and zinc (Zn), iron (Fe), magnesium (Mg), and potassium (K) are all higher than the control by 100%. Therefore, the purple wheat has obvious advantages in terms of the nutrient contents. Correlation analysis studies show that protein has significant positive correlations with Glu, Mo, Pro, Fe, Tyr and Ile. Anthocyanin has significant positive correlations with Mo and Glu, and significant negative correlations with free Trp and Ca. Carotenoid has significant positive correlations with His, Lys, Val, Leu, Arg, Gly and I, and significant negative correlations with Ca. This paper is a first report on comprehensive nutrients of several purple wheat lines. Our results suggest that purple wheat is rich in nutrients and there are many significant correlations among different nutrients. The valuable information is very useful in biofortification breeding and functional food development.

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