Reduced content of gamma-aminobutyric acid enhances resistance to bacterial wilt disease in tomato | Vien Khoa Hoc Ky Thuat Nong Nghiep Mien Nam

Reduced content of gamma-aminobutyric acid enhances resistance to bacterial wilt disease in tomato

Tuesday, 2024/12/17 | 08:21:15

Achen Zhao, Qiuyi Li, Pengfei Meng, Ping Liu, Siqun Wu, Zhaobo Lang, Yi Song, Alberto P. Macho

Plant Biotechnology Journal; 09 December 2024; https://doi.org/10.1111/pbi.14539

Summary

Bacteria within the Ralstonia solanacearum species complex cause devastating diseases in numerous crops, causing important losses in food production and industrial supply. Despite extensive efforts to enhance plant tolerance to disease caused by Ralstonia, efficient and sustainable approaches are still missing. Before, we found that Ralstonia promotes the production of gamma-aminobutyric acid (GABA) in plant cells; GABA can be used as a nutrient by Ralstonia to sustain the massive bacterial replication during plant colonization. In this work, we used CRISPR-Cas9-mediated genome editing to mutate SlGAD2, which encodes the major glutamate decarboxylase responsible for GABA production in tomato, a major crop affected by Ralstonia. The resulting Slgad2 mutant plants show reduced GABA content, and enhanced tolerance to bacterial wilt disease upon Ralstonia inoculation. Slgad2 mutant plants did not show altered susceptibility to other tested biotic and abiotic stresses, including drought and heat. Interestingly, Slgad2 mutant plants showed altered microbiome composition in roots and soil. We reveal a strategy to enhance plant resistance to Ralstonia by the manipulation of plant metabolism leading to an impairment of bacterial fitness. This approach could be particularly efficient in combination with other strategies based on the manipulation of the plant immune system, paving the way to a sustainable solution to Ralstonia in agricultural systems.

See https://onlinelibrary.wiley.com/doi/10.1111/pbi.14539

Figure 1

Generation and characterization of tomato Slgad2 mutant lines. (a) Summary of the mutations identified in tomato Slgad2 mutant lines. Mutations in the regions targeted by a single-guide RNA (sgRNA) are indicated, as well as the location of the mutations and resulting early stop codons. Numbers in the third column indicate the nucleotide positions in the SlGAD2 gene. Numbers in the fourth column indicate the nucleotide positions in the SlGAD2 coding region. A detailed diagram indicating the mutations is shown in Figure S3. (b) Outcome of the indicated mutations at the amino acid level. SlGAD2 contains a Glu-decarb-GAD domain (shown in red) and a calmodulin-binding domain (CaMBD, shown in blue). The numbers indicate the amino acid positions in the resulting proteins, and ‘M’ indicates methionine residues encoded by the original or alternative start codons. #1, #2, #3, #4, and #5 correspond to the five independent mutant lines. The lines with two arrowheads in blue and green represent the locations used to design primers for the qRT-PCR shown in panel (c). (c) qRT-PCR showing the expression of different SlGAD2 transcripts in tomato WT (Ailsa Craig, AC) and mutant plants. Tissues were collected from roots or leaves of 4-week-old tomato plants. Histograms with different colours correspond to results obtained using specific primers matching different RNAs, as indicated in panel (b): SlGAD2-up (shown in blue) corresponds to the RNA upstream of the mutation site in SlGAD2, and SlGAD2-down (shown in green) corresponds to the RNA downstream of the mutation site in SlGAD2. The specific primer hybridization sites are shown in Figure S4. Expression values were normalized to the expression of the housekeeping gene SlEF1α, and shown as relative to the expression in WT plants. Data from 3 independent biological repeats (n = 3 in each repeat) were pooled together and represented as mean ± SEM. Numbers indicate the P-values resulting from a Student t-test, comparing mutant and WT values.

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