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

Abstract

Plant antifungal proteins include the pathogenesis-related (PR)-5 family of fungi- and other stress-responsive thaumatin-like proteins (TLPs). However, the information on the TLPs of garlic (Allium sativum L.), which is often infected with soil Fusarium fungi, is very limited. In the present study, we identified 32 TLP homologs in the A. sativum cv. Ershuizao genome, which may function in the defense against Fusarium attack. The promoters of A. sativumTLP (AsTLP) genes contained cis-acting elements associated with hormone signaling and response to various types of stress, including those caused by fungal pathogens and their elicitors. The expression of AsTLP genes in Fusarium-resistant and -susceptible garlic cultivars was differently regulated by F. proliferatum infection. Thus, in the roots the mRNA levels of AsTLP7–9 and 21 genes were increased in resistant and decreased in susceptible A. sativum cultivars, suggesting the involvement of these genes in the garlic response to F. proliferatum attack. Our results provide insights into the role of TLPs in garlic and may be useful for breeding programs to increase the resistance of Allium crops to Fusarium infections.

Genome-Wide Identification, Expression, and Response to Fusarium Infection of the SWEET Gene Family in Garlic (Allium sativum L.)

“…The presence of hormone- and stress-responsive elements in AsSWEET promoters ( Figure 5 ) (which is also characteristic of garlic PR genes [ 54 , 55 , 56 ]) is consistent with the involvement of SWEETs in hormone-mediated as well as in hormone-independent signaling pathways regulating plant responses to abiotic and biotic stresses, including Fusarium infection [ 28 , 29 , 35 , 36 , 37 , 55 , 56 , 57 ].…”

“…Strelets) to FBR. The plants were infected with F. proliferatum and analyzed 24 and 96 h post-inoculation (hpi), covering the peak of pathogenesis-related (PR) gene expression in response to hemibiotrophic pathogens [ 55 , 56 , 57 , 58 ].…”

“…FBR of the bulbs and Fusarium wilt of the leaves can lead to significant (up to 60%) losses of the garlic crop [ 64 , 65 , 66 , 67 , 68 , 69 ]. F. proliferatum , one of the Fusarium species infecting garlic [ 57 ], is a common hemibiotrophic pathogen that utilizes plant sugars both in the biotrophic and necrotrophic phases [ 70 ]. Therefore, we hypothesized that this fungus could activate carbohydrate metabolism in garlic through the regulation of AsSWEET genes.…”

“…Earlier studies of FBR-resistant and -susceptible garlic cultivars have identified a set of A. sativum PR genes encoding chitinases, glucanases, and thaumatin-like proteins, which also have infection stage-dependent activation patterns and could be involved in anti-fungal immune defense [ 55 , 56 , 57 ]. Together with these findings, our present results suggest that AsSWEET genes can be a part of a complex protection system evolved in garlic to resist biotic as well as abiotic stresses, which requires further investigation.…”

Turning Garlic into a Modern Crop: State of the Art and Perspectives

“…F. proliferatum and F. oxysporum do not have a specific host [ 106 ], and intercropping with species that can be infected but are naturally resistant to these pathogens, such as maize and spring wheat [ 107 ], decreases inoculum levels in the soil [ 108 ]. Other gene families putatively involved in defense mechanisms against Fusarium infections have been identified in garlic, including genes that encode TLP (thaumatin-like proteins) [ 109 ], PR (pathogenesis-related) proteins [ 110 ] or CHI (class I chitinase) proteins [ 101 ], whose expression is positively correlated with the response to Fusarium in plants resistant to the fungus.…”