Narrow-Leafed Lupin (Lupinus angustifolius) β1- and β6-Conglutin Proteins Exhibit Antifungal Activity, Protecting Plants against Necrotrophic Pathogen Induced Damage from Sclerotinia sclerotiorum and Phytophthora nicotianae

Abstract

Vicilins (7S globulins) are seed storage proteins and constitute the main protein family in legume seeds, particularly in narrow-leafed lupin (Lupinus angustifolius L.; NLL), where seven vicilin genes, called β1- to β7-conglutin have been identified. Vicilins are involved in germination processes supplying amino acids for seedling growth and plant development, as well as in some cases roles in plant defense and protection against pathogens. The roles of NLL β-conglutins in plant defense are unknown. Here the potential role of five NLL β-conglutin family members in protection against necrotrophic fungal pathogens was investigated and it was demonstrated that recombinant purified 6xHis-tagged β1- and β6-conglutin proteins exhibited the strongest in vitro growth inhibitory activity against a range of necrotrophic fungal pathogens compared to β2, β3, and β4 conglutins. To examine activity in vivo, two representative necrotrophic pathogens, the fungus Sclerotinia sclerotiorum and oomycete Phytophthora nicotianae were used. Transient expression of β1- and β6-conglutin proteins in Nicotiana benthamiana leaves demonstrated in vivo growth suppression of both of these pathogens, resulting in low percentages of hyphal growth and elongation in comparison to control treated leaves. Cellular studies using β1- and β6-GFP fusion proteins showed these conglutins localized to the cell surface including plasmodesmata. Analysis of cellular death following S. sclerotiorum or P. nicotianae revealed both β1- and β6-conglutins suppressed pathogen induced cell death in planta and prevented pathogen induced suppression of the plant oxidative burst as determined by protein oxidation in infected compared to mock-inoculated leaves.

Irrigation affects characteristics of narrow-leaved lupin (Lupinus angustifolius L.) seeds

“…In general, these values are similar to the amount of protein present in soybeans (about 35%). The main proteins stored in the narrow, yellow, and white lupin seeds as well as in seeds of other legumes are globulins: γ-conglutin, β-conglutin (similar to vicilin), and α-conglutin (similar to legumin) (Lqari et al 2004;Sujak et al 2006;Duranti et al 2008;Foley et al 2015;Jimenez-Lopez et al 2016). Although the protein content (in mg/g of fresh weight) was comparable in the control and irrigated seeds, differences in the staining intensity of electrophoretically separated protein bands (especially the most strongly stained ones, which correspond to storage proteins) may indicate a possible difference in the quantitative proportions of particular types of storage proteins ( Fig.…”

Proteins in Relation to Vigor and Viability of White Lupin (Lupinus albus L.) Seed Stored for 26 Years

“…Moreover, these proteins probably participate in the signal transduction pathways, induce hypersensitivity reaction and strengthen the cell wall and cell membrane ( Ribeiro et al, 2014 ; De Oliveira Dias et al, 2015 ). Jimenez-Lopez et al (2016) have found that the β conglutins facilitate the oxidative burst, while at the same time they prevent its extinguishing and induction of apoptosis. The protective function of δ conglutins is also suggested by their similarity to the alpha-amylase inhibitor of cereal plants ( Duranti et al, 2008 ).…”

Narrow‐leafed lupin (Lupinus angustifolius L.) β‐conglutin: A multifunctional family of proteins with roles in plant defence, human health benefits, and potential uses as functional food

“…Furthermore, conglutins β1 and β6 suppressed pathogen‐induced cell death in planta. In addition, they inhibited pathogen‐induced suppression of the plant oxidative burst as determined by protein oxidation in infected plants (Jimenez‐Lopez et al, ), due to increased leves of pathogen‐ ( Sclerotinia sclerotiorum , P. nicotianae ) induced protein oxidation promoted by β1 and β6 while maintaining leaf health. This investigation provides the first demonstration for any NLL vicilin (β‐conglutins) of induced protection against pathogen attack.…”