Abstract
Sugarcane (Saccharum spp.) is a commercially important crop, vulnerable to fungal disease red rot caused by Colletotrichum falcatum Went. The pathogen attacks sucrose accumulating parenchyma cells of cane stalk leading to severe losses in cane yield and sugar recovery. We report development of red rot resistant transgenic sugarcane through expression of β-1,3-glucanase gene from Trichoderma spp. The transgene integration and its expression were confirmed by quantitative reverse transcription-PCR in first clonal generation raised from T0 plants revealing up to 4.4-fold higher expression, in comparison to non-transgenic sugarcane. Bioassay of transgenic plants with two virulent C. falcatum pathotypes, Cf 08 and Cf 09 causing red rot disease demonstrated that some plants were resistant to Cf 08 and moderately resistant to Cf 09. The electron micrographs of sucrose storing stalk parenchyma cells from these plants displayed characteristic sucrose-filled cells inhibiting Cf 08 hyphae and lysis of Cf 09 hyphae; in contrast, the cells of susceptible plants were sucrose depleted and prone to both the pathotypes. The transgene expression was up-regulated (up to 2.0-fold in leaves and 5.0-fold in roots) after infection, as compared to before infection in resistant plants. The transgene was successfully transmitted to second clonal generation raised from resistant transgenic plants. β-1,3-glucanase protein structural model revealed that active sites Glutamate 628 and Aspartate 569 of the catalytic domain acted as proton donor and nucleophile having role in cleaving β-1,3-glycosidic bonds and pathogen hyphal lysis.
Highlights
Sugarcane (Saccharum spp.) is a commercially important crop of tropical and sub-tropical regions cultivated primarily for production of sucrose, ethanol, biofuel and fibre-related commodities [1, 2]
The sucrose accumulating stalk parenchyma cells of these transgenic plants were intact and sucrose-filled, as trailing of fungal hyphae was either inhibited or hyphae were lysed, the transgene expression was upregulated after infection; and further, the active site residues involved in cleaving β-1,3-glycosidic bonds of C. falcatum hyphae were identified
The plants carrying red rot resistance had relatively high β1,3-glucanase transgene expression that was further up-regulated up to 2.0-fold in leaves and 5.0-fold in roots after C. falcatum infection as compared to before infection, pointing towards role of the transgene in plant defence mechanism in response to pathogen attack. β-1,3-glucanase expression has been demonstrated to be directly correlated with controlling disease incidence, such as in transgenic pearl millet expressing gluc78 [23] and transgenic canola carrying bgn13.1 [20]; and the transgene was induced upon pathogen infection [23]
Summary
Sugarcane (Saccharum spp.) is a commercially important crop of tropical and sub-tropical regions cultivated primarily for production of sucrose, ethanol, biofuel and fibre-related commodities [1, 2]. The cloning and characterization of β1,3-glucanase genes, such as bgn13.1 [18] and gluc78 [19] from Trichoderma spp. demonstrated inhibitory activity of the genes against phytopathogenic fungi. Their over-expression in transgenic plants resulted in imparting fungal resistance e.g. bgn13.1 expression in Brassica napus provided enhanced glucanase activity against Sclerotinia sclerotiorum [20], and displayed tolerance against C. acutatum and Rosellinia necatrix in strawberry [21]; likewise, gluc expression in rice provided resistance against Magnaporthe grisea [22], and Sclerospora graminicola in pearl millet [23]. There is no information in literature about expression of β-1,3-glucanase for resistance against fungal pathogens in sugarcane
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
