New progress in the regulatory mechanism of aluminum tolerance in Rhodomyrtus tomentosa via cell wall remodeling

Acidic soils account for approximately 40%-50% of the world's arable land, making them one of the major abiotic stress factors constraining agricultural production. In acidic soils, Al³⁺ inhibits root elongation and nutrient uptake, ultimately leading to significant crop yield losses. The plant cell wall serves as the first physical barrier against Al³⁺ entry, and its compositional modification plays a critical role in Al tolerance. The xyloglucan endotransglucosylase/hydrolase (XTH) family participates in plant stress responses by remodeling the xyloglucan network in the cell wall. However, the regulatory mechanisms of XTH genes in woody plant Al adaptation remain largely unclear.

Recently, a research team led by Prof. DENG Shulin from the South China Botanical Garden of the Chinese Academy of Sciences has revealed a novel RtERF1–RtXTH2 regulatory module that enhances aluminum tolerance in Rhodomyrtus tomentosa via cell wall remodeling, providing new insights into the molecular mechanisms of woody plant adaptation to acidic soils. The study was recently published in the journal The Plant Journal.

Rhodomyrtus tomentosa, a shrub widely distributed in tropical and subtropical regions, exhibits remarkable adaptability to acidic soils and represents an ideal material for studying the unique strategy of “turning toxicity into benefit” in plants. Nevertheless, how R. tomentosa perceives and responds to Al ions at the cell wall level, and the key genes and regulatory networks involved, have remained unclear.

Figure 1. RtERF1/RtXTH2 regulate Al tolerance in R. to tomentosa.（Image by DENG Faming）

The RtXTH (xyloglucan endotransglucosylase/hydrolase) family members play essential roles in cell wall restructuring through the modification or hydrolysis of xyloglucan chains, and thus play a crucial role in Al detoxification. Based on the genome and transcriptome, researchers identified the XTH gene family from R. tomentosa and found that RtXTH2 is significantly induced by Al in roots and shows the most prominent expression response. Further studies using transgenic Arabidopsis and VIGS (virus-induced gene silencing) in R. tomentosa demonstrated that RtXTH2 enhances Al tolerance by negatively regulating the abundance of Al-binding sites in the cell wall. To dissect the upstream regulatory network of RtXTH2, the team screened and identified RtERF1 as a transcription factor that significantly activates the promoter activity of RtXTH2. This study revealed that RtERF1 binds to CRT cis-elements in the promoter of RtXTH2, activating its transcription. The upregulated RtXTH2 then reduces hemicellulose and pectin content and thereby reduces Al³⁺ binding sites on the cell wall. Additionally, the researchers found that RtERF1 protein stability is enhanced under Al stress, suggesting the existence of post-translational regulatory mechanisms.

In summary, this study reveals the RtERF1–RtXTH2 transcriptional regulatory module in response to Al stress in R. tomentosa, providing a new framework for understanding cell wall remodeling-mediated Al adaptation in woody plants.

Figure 2. Proposed working model of the RtERF1–RtXTH2 regulatory module in response to Al stress in R. tomentosa.（Image by DENG Faming）

The study was supported by grants from the National Natural Science Foundation of China, the Guangdong Forestry Science and Technology Innovation Project, and the Guangdong Science and Technology Plan Project. Article link：https://doi.org/10.1111/tpj.70988