In this issue: Biotechnology Journal 9/2009

Using plant hormones in biotechnology Csukasi et al., Biotechnol. J. 2009, 4, 1293–130 Plant hormones have determinant roles in the final value of agricultural products since plant domestication. Therefore, advances in deciphering their structure, synthesis, perception and signaling pathways have been a main focus for research. Application of basic information on plant hormones in food quality and production has established some landmarks in plant biotechnology, e.g. from the dramatic increase in rice yield to long life tomatoes. The review presented by Victoriano Valpuesta and colleagues from Málaga, Spain, compiles all these success events in plant biotechnology when hormones are involved. In addition, future targets for genetic improvement are suggested after summarizing the most recent discoveries in the field. BRET assays in all colors Kamal et al., Biotechnol. J. 2009, 4, 1337–1344 G protein‐coupled receptors (GPCRs) play a central role in the signal transduction of an enormous array of biological stimuli. GPCR activation initiates their feedback desensitization mediated by GPCR kinases and β‐arrestin (β‐ARR) proteins. Researchers from France present and evaluate highly sensitive bioluminescence resonance energy transfer (BRET) assays with optimized donor/acceptor couples. Energy donors from Renilla luciferase (Rluc) were combined with the acceptors yellow fluorescent protein, the YPet variant and the Renilla green fluorescent protein (RGFP). Different donor/acceptor couples were tested in well‐established assays measuring ligand‐induced intramolecular rearrangements and recruitment to GPCRs. The results show increased sensitivity with Rluc8/YPet and Rluc8/RGFP couples and measured previously undetectable BRET signals. These tools improve existing β‐ARR assays and offer new options for the development of future BRET assays. Novel scFvs for biosensors Falco et al., Biotechnol. J. 2009, 4, 1328–1336 Single chain antibodies (scFvs) are synthetically constructed proteins that retain the antigen binding capacity of full‐length antibodies but are much smaller. Peter Berget and coworkers from Pittsburgh, USA have previously reported and characterized scFvs that are binding and activating several organic dyes, like thiazole orange or malachite green, causing them to fluoresce. Here they demonstrate that significant alteration of the fluorogenic dye activation can occur when different variable heavy (V H ) or variable light (V L ) domains are combined in the scFv format. Hybrid scFvs can be generated that have fluorogen‐activating domains that are completely inhibited by interactions with other domains. These new hybrid scFvs are members of a new class of two‐component fluoromolecules, which can be used to visualize cell‐surface proteins in mammalian cells. Moreover, they are excellent platforms for the development of genetically encoded, fluorescence‐generating biosensors.