Identification and characterization of gene sequences expressed in wheat spikelets at the heading stage.

Through differential analysis of transcripts (SDDM), 85 cDNA sequences specifically or preferentially expressed in wheat spikelets at heading time were identified and cloned; 54 of them had significant homology with genomic, cDNA and protein and 16 with EST sequences. Among these 54 clones, 44 matched genes with known functions, whereas 10 detected homology with putative genes encoding proteins whose functions have been deduced on the basis of bioinformatic comparisons. Seventeen clones corresponded to genes that had never been cloned in cereals, 5 were related to wheat genes with known functions, and the remaining 32 to genes cloned in other cereals. On the basis of their presumed functions, the 54 clones were assigned to seven groups. The first four of them contained 40 sequences likely involved in floral organ morphogenesis and gametogenesis, and precisely (i) sequences involved in the morphogenesis of floral organs; (ii) sequences expressed in pollen and/or anther tissues; (iii) sequences encoding transcription factors; (iv) sequences involved in signal perception and transduction (kinases and LRR proteins). The expression patterns of these 40 sequences have been studied by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of transcripts from different tissues and spike organs of wheat.