title: The last half-repeat of transcription activator-like effector (TALE) is dispensable and thereby TALE-based technology can be simplified.
abstract: To activate the expression of host genes that contribute to pathogen growth, pathogenic Xanthomonas bacteria inject their transcription activator-like effectors (TALEs) into plant cells and the TALEs bind to target gene promoters by the central repeat region consisting of near-perfect 34-amino-acid repeats (34-aa repeats). Based on the recognition codes between the 34-aa repeats and the targeted nucleotides, TALE-based technologies, such as designer TALEs (dTALEs) and TALE nucleases (TALENs), have been developed. Amazingly, every natural TALE invariantly has a truncated last half-repeat (LHR) at the end of the 34-aa repeats. Consequently, all the reported dTALEs and TALENs also harbour their LHRs. Here, we show that the LHRs in dTALEs are dispensable for the function of gene activation by both transient expression assays in Nicotiana benthamiana and gene-specific targeting in the rice genome, indicating that TALEs might originate from a single progenitor. In the light of this finding, we demonstrate that dTALEs can be constructed through two simple steps. Moreover, the activation strengths of dTALEs lacking the LHR are comparable with those of dTALEs harbouring the LHR. Our results provide new insights into the origin of natural TALEs, and will facilitate the simplification of the design and assembly of TALE-based tools, such as dTALEs and TALENs, in the near future.
authors: National Key Facility for Crop Gene Resources and Genetic Improvement (NFCRI), Key Laboratory of Crop Genetics and Breeding, Ministry of Agriculture, Institute of Crop Science, Chinese Academy of Agricultural Sciences (CAAS), Beijing, 100081, China.
authors: Chong-Ke
authors: CK
authors: Zheng
authors: Chun-Lian
authors: CL
authors: Wang
authors: Xiao-Ping
authors: XP
authors: Zhang
authors: Fu-Jun
authors: FJ
authors: Wang
authors: Teng-Fei
authors: TF
authors: Qin
authors: Kai-Jun
authors: KJ
authors: Zhao
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D018745:Genome, Plant; D005966:Glucuronidase / Q000235:genetics; D008969:Molecular Sequence Data; D012275:Oryza / Q000235:genetics; D020449:Repetitive Sequences, Amino Acid; D017386:Sequence Homology, Amino Acid; D014026:Nicotiana / Q000201:enzymology / Q000382:microbiology; D015534:Trans-Activators / Q000737:chemistry / Q000378:metabolism*; D014974:Xanthomonas / Q000378:metabolism / Q000472:pathogenicity
chemical_list: D001426:Bacterial Proteins; D015534:Trans-Activators; D005966:Glucuronidase
keywords: TAL effector; TALENs; dTALE; last half-repeat; unit assembly