Abstract
The basic β-1,3-glucanase of the carnivorous plant Drosera binata was tested as a purified protein, as well as under the control of a double CaMV35S promoter in transgenic tobacco for its capability to inhibit the growth of Trichoderma viride, Rhizoctonia solani, Alternaria solani, and Fusarium poae in an in-vitro assay. The purified protein inhibited tested phytopathogens but not the saprophytic fungus T. viride. Out of the analysed transgenic plants, lines 13, 16, 19, and 22 exhibited high DbGluc1 transcript abundance normalised to the actin transcript. Because of DbGluc1 transgene expression, lines 13 and 16 showed a 1.7-fold increase and lines 19 and 22 showed more than a 2-fold increase in total β-1,3-glucanase activity compared to the non-transgenic control. In accordance with the purified β-1,3-glucanase in-vitro antifungal assay, crude protein extracts of lines 19 and 22 significantly inhibited the growth of phytopathogens (14–34%). Further analyses revealed that the complementary action of transgenic β-1,3-glucanase and 20% higher activity of endogenous chitinase(s) in these lines were crucial for maximising the antifungal efficiency of crude protein extracts.
Highlights
Published: 23 August 2021 β-1,3-glucanases (E.C.3.2.1.39) catalyse the hydrolytic cleavage of the β-1,3-D-glycosidic linkages in β-1,3-glucans
The absorbance was measured at the start point (0 h) and the final point of cultivation, which was 24 h for F. poae and T. viride, 34 h for R. solani, and 40 h for A. solani
Comparison with the control showed that the purified β-1,3-glucanase effectively inhibited the growth of F. poae (24%), A. solani (14%), R. solani (17%) but not T. viride (Figure 1; Supplementary Table S2)
Summary
Published: 23 August 2021 β-1,3-glucanases (E.C.3.2.1.39) catalyse the hydrolytic cleavage of the β-1,3-D-glycosidic linkages in β-1,3-glucans. The first investigation of the Nicotiana tabacum genome revealed eight genes for acidic β-1,3-glucanases and four to six genes for basic β-1,3-glucanases [1,2]. Later it was shown that Arabidopsis thaliana and Zea mays genome contain even more complex gene families consisting of 50 and 71 putative genes, respectively [3,4]. Based on structural properties and cellular localisation, they are classified into five (I–V) classes in A. thaliana. All sequences contain an N-terminal signal peptide and glycosyl hydrolase family 17 domain. Classes I and II have one and class III has two carbohydrate binding modules (CBM43) that are responsible for binding to the substrate [3,5]
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