Pathogenesis-Related Genes of PR1, PR2, PR4, and PR5 Families Are Involved in the Response to Fusarium Infection in Garlic (Allium sativum L.)

Abstract

Plants of the genus Allium developed a diversity of defense mechanisms against pathogenic fungi of the genus Fusarium, including transcriptional activation of pathogenesis-related (PR) genes. However, the information on the regulation of PR factors in garlic (Allium sativum L.) is limited. In the present study, we identified AsPR genes putatively encoding PR1, PR2, PR4, and PR5 proteins in A. sativum cv. Ershuizao, which may be involved in the defense against Fusarium infection. The promoters of the AsPR1–5 genes contained jasmonic acid-, salicylic acid-, gibberellin-, abscisic acid-, auxin-, ethylene-, and stress-responsive elements associated with the response to plant parasites. The expression of AsPR1c, d, g, k, AsPR2b, AsPR5a, c (in roots), and AsPR4a(c), b, and AsPR2c (in stems and cloves) significantly differed between garlic cultivars resistant and susceptible to Fusarium rot, suggesting that it could define the PR protein-mediated protection against Fusarium infection in garlic. Our results provide insights into the role of PR factors in A. sativum and may be useful for breeding programs to increase the resistance of Allium crops to Fusarium infections.

Thaumatin-like Protein (TLP) Genes in Garlic (Allium sativum L.): Genome-Wide Identification, Characterization, and Expression in Response to Fusarium proliferatum Infection

“…The promoters of all PR5 family AsTLP genes contained cis -regulatory elements associated with the activation of immune mechanisms through responses to stresses (anaerobic conditions, dehydration, low temperature, salinization, heavy metals, and wounding), elicitors, and hormones, ( Figure 6 ). A similar set of elements has also been found in the promoters of Gossypium barbadense and Rosa chinensis TLP genes [ 73 , 74 ] and of the other garlic PR1–5 genes [ 50 , 60 ]. Accordingly, the expression of AsTLP genes may be triggered by phytohormones (ethylene, salicylic acid, ABA, and MeJA), and stresses.…”

“…by, for example, generating cultivars that overexpress the respective AsTLP genes, which may protect against fungal infections. In addition, it should be noted that, besides TLPs, the fungicidal effects of Allium plants are associated with chitinases and endo-1,3-β-glucanases, as well as miRNAs involved in positive (miR164a, miR168a, and miR393) and negative (miR394) regulation of resistance to Fusarium [ 48 , 50 , 60 , 78 ]. Moreover, Allium roots produce antifungal volatiles such as 2-methyl-2-pentenal and organosulfur compounds, as well as non-volatiles such as spirostanol, furostanol, and steroidal saponins, which inhibit Fusarium growth [ 60 , 79 , 80 ].…”

“…The strain was originally isolated from the bulbs of garlic cv. Strelets; according to the pathogenicity test, the first signs of the disease appeared on the clove surface 5 days after infection [ 50 ].…”

“…Given that in Arabidopsis , PR5 expression confers resistance to a necrotrophic fungus B. cinerea , it can be suggested that AsPR5 plays a similar role in garlic through regulation of signaling pathways associated with antifungal defense. The other three identified garlic TLP-coding genes, AsPR5a (Asa2G01043.1), AsPR5b (Asa4G02099.1), and AsPR5c (Asa4G02100.1) have been reported to be differentially expressed in the roots of FBR-resistant and -susceptible garlic cultivars in response to F. proliferatum attack [ 50 ].…”

Genome-wide Identification and Characterization of the GRAS Transcription Factors in Garlic (Allium sativum L.)

“…Recently, the assembly of garlic genome was completed using a repertoire of five advanced sequencing methodologies ( Sun et al, 2020 ), which made it feasible to identify the genes important for garlic growth and development in Allium crops. Consequently, several gene families, such as GH19, PR, and KNOX, have been systemically characterized ( Anisimova et al, 2021 ; Filyushin et al, 2021 ; Zhang et al, 2021 ). The GRAS family is one of the most important transcription factor families that participate widely in the plant growth regulation and development.…”