Abstract:

【Objective】 The objective of this study is to develop an EST database of wheat infected by avirulent Puccinia triticina isolate and provide a base for understanding the wheat resistant mechanism to the pathogen at the molecular level. 【Method】The positive clones of TcLr19 cDNA library from wheat leaves induced by P. triticina were picked up randomly for sequencing, and the qualified expressed sequence tags (ESTs) were annotated. The functional classification of all ESTs was established based on the database entry giving the best E-value using the Bevan's classification categories. The expression profiles of two signal transduction genes and three disease/defence genes were analyzed by normalization with Actin.【Result】 Seven hundred and fifty-six clones of the cDNA library were sequenced randomly, and 649 qualified ESTs were acquired and clusterted into 472 unisequences. All ESTs were classified, 25.2% of these genes were similar to genes encoding proteins with unknown functions, and 21.0% genes shared high homology with genes involved in energy metabolism and photosynthesis. And 17.8% of the genes with functions related to disease defence and signal transduction, and those in the remaining groups to genes involved in transcription, transport processes, protein metabolism, etc, respectively. The results of RT-PCR showed that the transcripts of the selected genes were different at different time points of wheat leaves after inoculated with the pathogen, and the expression patterns of each gene were inconsistent in wheat leaves. 【Conclusion】The putative calcium-transporting ATPase, glutathione-S-transferase, putative protein kinase Pti1, NBS-LRR disease resistance protein homologue, Chaperone protein DnaJ, etc., were supposed to involve in the process of the incompatible interaction between wheat TcLr19 and the P. triticina race. The cDNA library is useful for identifying the functional genes involved in the wheat-leaf rust incompatible interaction, and thus laying a foundation for establiment of a new database for studying leaf rust pathogenesis genes and wheat defense genes.

Key words: wheat, Puccinia triticina, cDNA library, expressed sequence tag (EST)