Genome-wide characterization, transcriptome profiling, and functional analysis of the ALMT gene family in Medicago for aluminum resistance

Dehui Jin; Jinlong Chen; Yumeng Kang; Fang Yang; Dongwen Yu; Xiaoqing Liu; Chengcheng Yan; Zhenfei Guo; Yang Zhang

doi:10.1016/j.jplph.2024.154262

Genome-wide characterization, transcriptome profiling, and functional analysis of the ALMT gene family in Medicago for aluminum resistance

J Plant Physiol. 2024 Apr 29:297:154262. doi: 10.1016/j.jplph.2024.154262. Online ahead of print.

Authors

Dehui Jin¹, Jinlong Chen¹, Yumeng Kang¹, Fang Yang¹, Dongwen Yu¹, Xiaoqing Liu¹, Chengcheng Yan¹, Zhenfei Guo², Yang Zhang³

Affiliations

¹ College of Grassland Science, Nanjing Agricultural University, Nanjing, Jiangsu, China.
² College of Grassland Science, Nanjing Agricultural University, Nanjing, Jiangsu, China. Electronic address: zfguo@njau.edu.cn.
³ College of Grassland Science, Nanjing Agricultural University, Nanjing, Jiangsu, China. Electronic address: yzhang@njau.edu.cn.

PMID: 38703548
DOI: 10.1016/j.jplph.2024.154262

Abstract

Aluminum (Al) is the major limiting factor affecting plant productivity in acidic soils. Al³⁺ ions exhibit increased solubility at a pH below 5, leading to plant root tip toxicity. Alternatively, plants can perceive very low concentrations of Al³⁺, and Al triggers downstream signaling even at pH 5.7 without causing Al toxicity. The ALUMINUM-ACTIVATED-MALATE-TRANSPORTER (ALMT) family members act as anion channels, with some regulating the secretion of malate from root apices to chelate Al, which is a crucial mechanism for plant Al resistance. To date, the role of the ALMT gene family within the legume Medicago species has not been fully characterized. In this study, we investigated the ALMT gene family in M. sativa and M. truncatula and identified 68 MsALMTs and 18 MtALMTs, respectively. Phylogenetic analysis classified these genes into five clades, and synteny analysis uncovered genuine paralogs and orthologs. The real-time quantitative reverse transcription PCR (qRT-PCR) analysis revealed that MtALMT8, MtALMT9, and MtALMT15 in clade 2-2b are expressed in both roots and root nodules, and MtALMT8 and MtALMT9 are significantly upregulated by Al in root tips. We also observed that MtALMT8 and MtALMT9 can partially restore the Al sensitivity of Atalmt1 in Arabidopsis. Moreover, transcriptome analysis examined the expression patterns of these genes in M. sativa in response to Al at both pH 5.7 and pH 4.6, as well as to protons, and found that Al and protons can independently induce some Al-resistance genes. Overall, our findings indicate that MtALMT8 and MtALMT9 may play a role in Al resistance, and highlight the resemblance between the ALMT genes in Medicago species and those in Arabidopsis.

Keywords: ALMT; Aluminum resistance; Aluminum treatment at high pH; Malate; Medicago; Transcriptome.