Transcriptome responses to Ralstonia solanacearum infection in tetraploid potato

Abstract

Potato (Solanum tuberosum) is an important global food source, the growth of which can be severely impacted by Ralstonia solanacearum bacterial infection. Despite extensive research, the molecular mechanisms of potato resistance to this pathogen are imperfectly known. Huashu No. 12, a tetraploid potato genotype, is highly resistant to R. solanacearum. We inoculate Huashu No. 12 and Longshu No. 7 (highly susceptible to R. solanacearum) with R. solanacearum to compare disease resistance in these two potato varieties. Huashu No. 12 has significantly higher resistance to R. solanacearum infection than Longshu No. 7, with increased lignin content, and an abundance of callose and strong autofluorescence in the phloem sieve tube. Enzymes (e.g., superoxide dismutase, catalase, peroxidase, phenylalanine ammonia-lyase, and polyphenol oxidase) contribute to R. solanacearum resistance in Huashu No. 12. Transcriptome sequencing reveals 659 differentially expressed genes between the two varieties, with the ethylene responsive factor family containing the most differentially expressed genes. Gene ontology and KEGG analyses provided further insights into the genetic basis and molecular mechanisms underlying plant defense against R. solanacearum disease. By demonstrating the importance of enzymes and differential gene expression in Huashu No. 12 resistance to R. solanacearum infection, the breeding of disease-resistant potato becomes increasingly feasible.

Keywords: Differentially expressed genes; Disease resistance; Potato; RNA-Seq; Ralstonia solanacearum.

Fig. 1

A, disease index investigation following inoculation with Ralstonia solanacearum to Huashu No. 12 and Longshu No. 7; and incidence of R. solanacearum at 0, 2, 4, 6, 8, 10, 12, 14, 16 and 18 days post inoculation in B, Huashu No. 12, and C, Longshu No. 7.

Fig. 2

Observation of lignin contents at the stem base at 0 and 7 days post inoculation with Ralstonia solanacearum.

Fig. 3

Callose distribution at the base of the stem at 2 days post inoculation with Ralstonia solanacearum: A, C, E, Huashu No. 12; and B, D, F, Longshu No. 7.

Fig. 4

Changes in A, catalase (CAL); B, peroxidase (PAL); C, POD (phenylalanine ammonia-lyase); D, polyphenol oxidase (PPO); and E, superoxide dismutase (SOD) following inoculation with Ralstonia solanacearum.

Fig. 5

Numbers of differentially expressed genes.

Fig. 6

Venn diagram of differentially expressed genes (0, 24, and 48 hpi).

Fig. 7

Gene ontology analysis of differentially expressed genes.

Fig. 8

A, KEGG classification map of differentially expressed genes; B, pathway analysis of differentially expressed genes.

Fig. 9

Number of transcription factors in different families that were differentially expressed following inoculation with Ralstonia solanacearum.

Fig. 10

qRT-PCR verification.