Transgenic rice expressing <it>Allium sativum </it>leaf agglutinin (ASAL) exhibits high-level resistance against major sap-sucking pests

• Main Authors: Vudem Dasavantha, Immanni China, Sadumpati Vijayakumar, Yarasi Bharathi, Khareedu Venkateswara
• Format: Article
• Language: English
• Published: BMC 2008-10-01
• Series: BMC Plant Biology
• Online Access: http://www.biomedcentral.com/1471-2229/8/102

<p>Abstract</p> <p>Background</p> <p>Rice (<it>Oryza sativa</it>) productivity is adversely impacted by numerous biotic and abiotic factors. An approximate 52% of the global production of rice is lost annually owing to the damage caused by biotic factors, of which ~21% is attributed to the attack of insect pests. In this paper we report the isolation, cloning and characterization of <it>Allium sativum </it>leaf agglutinin (<it>asal</it>) gene, and its expression in elite indica rice cultivars using <it>Agrobacterium</it>-mediated genetic transformation method. The stable transgenic lines, expressing ASAL, showed explicit resistance against major sap-sucking pests.</p> <p>Results</p> <p><it>Allium sativum </it>leaf lectin gene (<it>asal</it>), coding for mannose binding homodimeric protein (ASAL) from garlic plants, has been isolated and introduced into elite indica rice cultivars susceptible to sap-sucking insects, viz., brown planthopper (BPH), green leafhopper (GLH) and whitebacked planthopper (WBPH). Embryogenic calli of rice were co-cultivated with <it>Agrobacterium </it>harbouring pSB111 super-binary vector comprising garlic lectin gene <it>asal </it>along with the herbicide resistance gene <it>bar</it>, both under the control of CaMV35S promoter. PCR and Southern blot analyses confirmed stable integration of transgenes into the genomes of rice plants. Northern and western blot analyses revealed expression of ASAL in different transgenic rice lines. In primary transformants, the level of ASAL protein, as estimated by enzyme-linked immunosorbent assay, varied between 0.74% and 1.45% of the total soluble proteins. <it>In planta </it>insect bioassays on transgenic rice lines revealed potent entomotoxic effects of ASAL on BPH, GLH and WBPH insects, as evidenced by significant decreases in the survival, development and fecundity of the insects.</p> <p>Conclusion</p> <p><it>In planta </it>insect bioassays were carried out on <it>asal </it>transgenic rice lines employing standard screening techniques followed in conventional breeding for selection of insect resistant plants. The ASAL expressing rice plants, bestowed with high entomotoxic effects, imparted appreciable resistance against three major sap-sucking insects. Our results amply demonstrate that transgenic indica rice harbouring <it>asal </it>exhibit surpassing resistance against BPH, GLH and WBPH insects. The prototypic <it>asal </it>transgenic rice lines appear promising for direct commercial cultivation besides serving as a potential genetic resource in recombination breeding.</p>