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.
Highlights
IntroductionOne of the most harmful pathogens is fungi, which developed many sophisticated mechanisms to penetrate and colonize host cells, including hydrolysis of the plant cell wall with pectinases, cellulases, and proteases [4]
We performed in silico identification and characterization of the genes belonging to the PR1, PR2, PR4, and PR5 families in the A. sativum genome and studied their tissue expression patterns in Fusarium basal rot (FBR)-resistant and susceptible garlic cultivars infected with F. proliferatum
Our results indicate that the promoters of the AsPR genes contain 15 cis-regulatory elements involved in the response to hormones such as abscisic acid (ABA), salicylic acid (SA), MeJA, auxin, ET, and gibberellic acid (GA), as well as 12 elements associated with immune defense and response to elicitors and stresses such as anaerobic conditions, dehydration, low and high temperature, salinization, heavy metals, and wounding (Table 3)
Summary
One of the most harmful pathogens is fungi, which developed many sophisticated mechanisms to penetrate and colonize host cells, including hydrolysis of the plant cell wall with pectinases, cellulases, and proteases [4]. The plant cell wall, containing cutin, wax, and lignin, represents the first line of defense against invading pathogens [2]. If it is broken, the plant immune system, which is the second line of defense, is activated through plant receptors that perceive pathogen-associated molecular patterns, including flagellins and components of the fungal cell wall, such as lipopolysaccharides, chitin, and branched β-glucans [5], as well as through the mobilization of resistance-related proteins that recognize pathogen effectors [6]. The SA pathway, triggered mainly by biotrophic pathogens, is involved in systemic acquired resistance (SAR), which induces the expression of the PR1, PR2, and PR5 genes and prevents the spread of infection to healthy tissues [2], whereas the JA pathway, mainly activated by necrotrophic pathogens, provides local acquired resistance (LAR) through the upregulation of PR3, PR4, and PR12 genes [2]
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