Tillering in wheat is a critical agronomic trait that affects the grain yield. Molecular mechanisms that control the architecture in wheat are still not fully understood. Identifying genes which are involved in regulation of tillering in wheat are of great interest. Ideal Plant Architecture 1 (IPA1) gene, reported as a negative regulator of tiller number in rice, function as a downstream transcription factor repressed by D53 in strigolactone induced gene expression. Rice IPA1 orthologues in wheat can act as strong candidates for genes regulating tillering in wheat. Therefore, we identified orthologous genes of IPA1 in wheat, exploring the opportunity to understand genetic information and functional links between tillering and IPA1 gene leading to yield changes associated with it. Genomic information about the IPA1 gene in rice was collected from Rice Genome Annotation Project and was used as a query for homology-based searches against the wheat genomic sequence database in URGI. Three candidate genes for wheat IPA1, which are present on group 7 homoeologous chromosomes (7A, 7B & 7D) were selected. The candidate genes belong to the same SBP protein family of the rice IPA1 gene. The predicted gene structures revealed that all the candidate genes contain three exons. The sequences of IPA1 candidate genes were highly conserved across the genomes 15 wheat cultivars available on Ensembl Plants database. The IPA1 candidate genes were amplified and sequenced from Unnat-PBW550, a low tillering variety from Punjab. The deduced proteins of TaIPA1-7A (386 aa) TaIPA1-7B (393 aa) and TaIPA-7D (395 aa) were highly similar (>93-94%) and exhibit >59-61% similarity with rice IPA1 protein. The expression patterns of IPA1 candidate genes in various tissues (root, shoot/leaf, spike, grain) at three developmental stages (seedling, vegetative and reproductive) were studied for Chinese spring and Azhurnaya from wheat expression database (www.wheat-expression.com). Our initial results showed that the candidate genes are expressed mostly in stem and spikes at Z30 and Z32 (Zadok’s growth scale) stages respectively. For functional validation CRISPR-Cas9 based editing of IPA1 candidate genes in wheat is being carried out.
