Special Abstracts / Journal of Biotechnology 150S (2010) S1–S576 S115

an extensive framework for new applied biotech tools. Althoughcrop innovation and crop protection are based on general appliedbiotech principles, they must be adapted locally and be linked tothe problems, priorities and local constraints of researchers andfarmers.Rice and its pathogen Xanthomonas oryzae pv. oryzae (Xoo)provide an excellent example to assess the status and potential ofbiotech tools and their delivery into useful products in the field.During the last decade, the culture of rice has drastically increasedin West-Africa, and Xoo, the causal agent of rice bacterial blight, hasconcomitantly increased in most West-African rice growing areasbased on recent reports. Yield losses caused by Xoo range from 20 to30% and can be as high as 50% in some areas. The disease is expand-ing to new rice-cultivated areas and represents a significant threatto food security in the region. The use of resistant cultivars is stillthe most economical and effective way to control this disease. Tofacilitate development of and strategic deployment of rice culti-vars with resistance to bacterial blight, biotechnology tools andapproaches, including marker-assisted breeding, gene combina-tions for disease control, and multiplex-PCR for pathogen diagnosis,have been developed. Although these technologies are routinelyused in Asia and the USA, their application in West-Africa remainslimited. Major challenges to their implementation in Africa areoften the costs and the sophistication of the techniques required.Thus, developers of the technologies at research institutions needto work with end users from an early stage to create and pro-mote the integration of successful, low cost applications of researchbiotech products. In this presentation we will give examples of thedifferent biotechnologies available in our laboratories and others,or currently being developed to improve disease control. We willalso discuss how to facilitate their application and delivery to thefield. Improving the transfer of biotechnologies through existinglaboratory hubs in Africa should greatly benefit African farmersby improving their ability to combat this economically importantplant disease.

doi:10.1016/j.jbiotec.2010.08.296

[P&F.19]

Quorum sensing effects on Pseudomonas corrugata plant inter-action and antagonistic activity

Grazia Licciardello 1,2,∗, Iris Bertani 3, Laura Steindler 3, PatriziaBella 2, Vittorio Venturi 3, Vittoria Catara 2

1 Scientific and Technology Park of Sicily, Italy2 Department of Phytosanitary Science and Technologies, Italy3 Bacteriology Group, International Centre for Genetic Engineering andBiotechnology, ItalyKeywords: Quorum sensing; Pseudomonas corrugata; Tomato pithnecrosis; Regulation

Quorum sensing (QS) is a cell-density dependent regulatory sys-tem, which in Pseudomonas spp. controls the expression of genesinvolved in virulence, biocontrol and ecological fitness. We investi-gated the role of QS in the phytopathogenic bacterium P. corrugata,causal agent of tomato pith necrosis. The genetic system PcoI-PcoRcodifies for the LuxR transcriptional activator PcoR and the PcoIautoinducer synthase (LuxI family) responsible of the synthesisof N-acyl-homoserine lactones (AHLs) molecular signals. Analysisof knock-out mutants showed that QS is involved in virulence ontomato and in vitro antagonistic activity against a number of fungiand bacteria. In particular, QS seems to be involved in the regula-tion of lipodepsipeptide (LDP) production, a key virulence factorin tomato necrosis. We found that LDP production is cell-density-dependent.

Further sequencing revealed that pcoI gene is co-transcribedwith rfiA and is directly linked to QS. The deduced RfiA codifiesfor a transcriptional regulator belonging to the LuxR family pro-tein that, differently to PcoR, does not contain an autoinducerbinding domain. We also identified downstream rfiA, an operon,designated pcoABC, encoding for a tripartite resistance nodulation-cell-division (RND) transporter system, partially involved in thesecretion of LDP. Transcriptional analysis revealed that the expres-sion of pcoABC is controlled by RfiA and QS by a hierarchicalregulatory system.

Knock-out mutants analysis showed that RfiA has a crucial rolein P. corrugata/plant interaction. In fact, RfiA inactivation drasticallyreduced necrosis development in tomato pith and inhibited antago-nistic activity related to LDP production in vitro. Tomato inoculationwith different mutants revealed that in presence of AHLs, PcoR acti-vates gene expression of virulence factors via RfiA. However, PcoR,in absence of AHL signals, can induce virulence gene expression viaanother yet unknown mechanism.

doi:10.1016/j.jbiotec.2010.08.297

[P&F.20]

Stress tolerance and grain yield of transgenic rice plants

J.S. Jeong 1, Y.S. Kim Kim 1, Y.D. Choi 2, M.K. Kim 2, J.K. Kim 1,∗

1 Myongji University, Korea, Republic of2 Seoul National University, Korea, Republic ofKeywords: Drought tolerance; Transgenic rice; OsNAC10; Field test

Drought poses a serious threat to the sustainability of riceyields in rainfed agriculture. Here we report the results of a func-tional genomics approach that identified a rice NAC-domain gene,OsNAC10, which improved performance of transgenic rice plantsunder field drought conditions. A group of OsNAC genes were pre-screened for enhanced stress tolerance when overexpressed in rice.The OsNAC10, one of the effective members selected from pre-screening, is expressed predominantly in roots and panicles, andinduced by drought, high salinity and abscisic acid. Overexpressionof OsNAC10 in rice under the control of the constitutive promoterGOS2 and the root-specific promoter RCc3 increased the plant toler-ance to drought, high salinity and low temperature at the vegetativestage. More importantly, the RCc3:OsNAC10 plants showed sig-nificantly enhanced drought tolerance at the reproductive stage,increasing grain yield by 25-42% and 5-14% over controls in the fieldunder drought and normal conditions, respectively. Grain yield ofGOS2:OsNAC10 plants in the field, in contrast, remained similar tothat of controls under both normal and drought conditions. Thesedifferences in performance under field drought conditions reflectthe difference in expression of OsNAC10-dependent target genes inroots as well as in leaves of the two transgenic plants, as revealedby microarray analyses. Root diameter of the RCc3:OsNAC10 plantswas thicker by 1.25-fold than that of the GOS2:OsNAC10 and NTplants due to the enlarged stele, cortex and epidermis. Overall, ourresults demonstrated that root specific overexpression of OsNAC10enlarges roots, enhancing drought tolerance of transgenic plants,which increases grain yield significantly under field drought con-ditions.

doi:10.1016/j.jbiotec.2010.08.298