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Key message <p>The overexpression of <i>MdDIR7</i> can alleviate osmotic and oxidative damage, increase the expression of <i>MdFRO2</i> and<i> MdIRT1</i>, and improve plant performance under Fe-deficient conditions.</p> Abstract <p>Iron (Fe) is an essential trace element that serves as a critical component in numerous cellular processes, such as photosynthesis, respiration, and nitrogen-sulfur assimilation. Fe deficiency commonly occurs in alkaline and calcareous soils worldwide and severely affects plant growth and development. Members of the Dirigent (DIR) family have been identified and shown to play a role in abiotic stress response in several species, but have not been identified in apple and whether they also play an important role in Fe-deficiency stress has not been revealed. In this study, 41 members of the DIR family were identified from the apple genome, and they were unevenly distributed across 12 chromosomes of the apple (not distributed on chromosome 8). Real-time fluorescence quantitative PCR (RT-qPCR) indicated that the expression levels of the MdDIR7 gene in the leaves and roots of <i>Malus hupehensis</i> were significantly higher than those of the other members of this family under Fe-deficiency stress. Therefore, MdDIR7 was selected for further functional analysis using stable transformation, root transformation, and virus-induced gene silencing (VIGS). The results showed that root overexpression of MdDIR7 significantly increased photosynthetic pigment contents and improved chlorophyll fluorescence parameters, reduced relative electrical conductivity (REC) and malondialdehyde (MDA) content, increased antioxidant enzyme activity (SOD, CAT), reduced the accumulation of reactive oxygen species (ROS), and was associated with Fe-deficiency stress. Similar results were also observed in apple calli. On the contrary, we found that silenced MdDIR7 (TRV-MdDIR7) under the stress led to greater damage than the TRV plants. In addition, root overexpression of MdDIR7 upregulated the expression of Fe uptake-related genes MdFRO2 and MdIRT1 and significantly increased total Fe content, whereas silencing of MdDIR7 downregulated the expression of MdFRO2 and MdIRT1. In summary, the overexpression of MdDIR7 gene was associated with improved performance under Fe-deficiency conditions.</p>

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Identification of Dirigent (DIR) genes in apple (Malus domestica) displays the role of MdDIR7 in iron (Fe)-deficiency stress tolerance

  • 期刊论文

  • 发表日期：

    2026年8月3日

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  • Wenbo Li,
  • Zhongxing Zhang,
  • Lanlan Hao,
  • Yanlong Gao,
  • Xulin Xian,
  • Yanxiu Wang

摘要

Key message

The overexpression of MdDIR7 can alleviate osmotic and oxidative damage, increase the expression of MdFRO2 and MdIRT1, and improve plant performance under Fe-deficient conditions.

Abstract

Iron (Fe) is an essential trace element that serves as a critical component in numerous cellular processes, such as photosynthesis, respiration, and nitrogen-sulfur assimilation. Fe deficiency commonly occurs in alkaline and calcareous soils worldwide and severely affects plant growth and development. Members of the Dirigent (DIR) family have been identified and shown to play a role in abiotic stress response in several species, but have not been identified in apple and whether they also play an important role in Fe-deficiency stress has not been revealed. In this study, 41 members of the DIR family were identified from the apple genome, and they were unevenly distributed across 12 chromosomes of the apple (not distributed on chromosome 8). Real-time fluorescence quantitative PCR (RT-qPCR) indicated that the expression levels of the MdDIR7 gene in the leaves and roots of Malus hupehensis were significantly higher than those of the other members of this family under Fe-deficiency stress. Therefore, MdDIR7 was selected for further functional analysis using stable transformation, root transformation, and virus-induced gene silencing (VIGS). The results showed that root overexpression of MdDIR7 significantly increased photosynthetic pigment contents and improved chlorophyll fluorescence parameters, reduced relative electrical conductivity (REC) and malondialdehyde (MDA) content, increased antioxidant enzyme activity (SOD, CAT), reduced the accumulation of reactive oxygen species (ROS), and was associated with Fe-deficiency stress. Similar results were also observed in apple calli. On the contrary, we found that silenced MdDIR7 (TRV-MdDIR7) under the stress led to greater damage than the TRV plants. In addition, root overexpression of MdDIR7 upregulated the expression of Fe uptake-related genes MdFRO2 and MdIRT1 and significantly increased total Fe content, whereas silencing of MdDIR7 downregulated the expression of MdFRO2 and MdIRT1. In summary, the overexpression of MdDIR7 gene was associated with improved performance under Fe-deficiency conditions.