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Knowledge and technology transfer to African laboratories and farmers is an important objective for achieving food security and sustainable crop production on the sub-Saharan African continent. Cassava (Manihot esculenta Crantz) is a vital source of calories for more than a billion people in developing countries, and its potential industrial use for starch and bioethanol in the tropics is increasingly being recognized. However, cassava production remains constrained by the susceptibility of the crop to several biotic and abiotic stresses. For more than a decade, biotechnology has been considered an attractive tool to improve cassava as it substantially circumvents the limitations of traditional breeding, which is particularly time-consuming and tedious because of the high heterozygosity of the crop. A major constraint to the development of biotechnological approaches for cassava improvement has been the lack of an efficient and robust transformation and regeneration system. Despite some success achieved in genetic modification of the model cassava cultivar Tropical Manihot Series (TMS), TMS 60444, in some European and U.S. laboratories, the lack of a reproducible and robust protocol has not allowed the establishment of a routine transformation system in sub-Saharan Africa. In this study, we optimized a robust and efficient protocol developed at ETH Zurich to successfully establish transformation of a commercially cultivated South African landrace, T200, and compared this with the benchmark model cultivar TMS 60444. Results from our study demonstrated high transformation rates for both T200 (23 transgenic lines from 100 friable embryogenic callus (FEC) clusters) compared with TMS 60444 (32 transgenic lines from 100 FEC clusters). The success in transforming landraces or farmer-preferred cultivars has been limited, and the high transformation rate of an industry-preferred landrace in this study is encouraging for a feasible transformation program for cassava improvement in South Africa (SA), which can potentially be extended to other countries in southern Africa. The successful establishment of a robust cassava transformation and regeneration system in SA demonstrates the relevance of technology transfer to sub-Saharan Africa and highlights the importance of developing suitable and reliable techniques before their transfer to laboratories offering less optimal conditions. [Copyright &y& Elsevier]

Abstract: The chloroplast 24 kDa RNA binding protein (24RNP) from Spinacea oleracea is a nuclear encoded protein that binds the 3′ untranslated region (3′UTR) of some chloroplast mRNAs and seems to be involved in some processes of mRNA metabolism, such as 3′UTR processing, maturation and stabilization. The 24RNP is similar to the 28RNP which is involved in the correct maturation of petD and psbA 3′UTRs, and when phosphorylated, decreases its binding affinity for RNA. In the present work, we determined that the recombinant 24RNP was phosphorylated in vitro either by an animal protein kinase C, a plant Ca2+-dependent protein kinase, or a chloroplastic kinase activity present in a protein extract with 3′-end processing activity in which the 24RNP is also present. Phosphorylation of 24RNP increased the binding capacity (B max) 0.25 time for petD 3′UTR, and three times for psbA 3′UTR; the affinity for P-24RNP only increased when the interaction with petD was tested. Competition experiments suggested that B max, not K d, might be a more important factor in the P-24RNP-3′UTR interaction. The data suggested that the 24RNP role in chloroplast mRNA metabolism may be regulated in vivo by changes in its phosphorylation status carried out by a chloroplastic kinase. [Copyright &y& Elsevier]