Fusarium pseudograminearum anti-apoptosis gene FpBir1 is required for conidiation and pathogenesis
Linlin Chen: Department of Plant Pathology,Henan Agricultural University
<div>Apoptosis plays crucial roles in physiological processes from development to adaptive responses. Certain aspects of apoptosis have been recently verified in eukaryotic microbes, but not in <em>Fusarium</em> species yet. Here we identified a <em>FpBir1</em> in <em>Fusarium pseudograminearum</em>, a homolog of <em>Saccharomyces cerevisiae</em> BIR1 which is the unique inhibitors of apoptosis protein. Two BIR domains at the N terminal of FpBir1 protein were identified. <em>FpBir1</em> was up-regulated during both early and later infection. Compared with the infection on susceptible wheats at early stage which is over-expressed approximately 3-fold,<em> FpBir1</em> was induced over 5-fold in the incompatible interaction. Two <em>FpBir1</em> deletion mutants were obtained by the PEG-mediated protoplast stable transformation, and more apoptosis cells were observed in ∆<em>fpbir1</em>. ∆<em>fpbir1</em> mutated mycelia showed similar growth rates to that of WT, but was thinner and less branched under microscopic examination. Conidia of ∆<em>fpbir1 </em>was much less than that of the WT, and only 24% of the mutants conidia was visible or germinated very short germ tubes at 6 h, while approximately 50% of WT conidia had germinated and produced germ tubes longer than the width of conidia under the same conditions. Furthermore, deletion of <em>FpBir1</em> gene reduced the virulence in the compatible interaction. Upon the wheat coleoptiles infected with mycelia, the lesion sizes of ∆<em>fpbir1</em>were reduced to 50% of WT at 3 dpi. Under a pot inoculation experiment, the wheat seedlings inoculated with ∆<em>fpbir1</em> remained healthy at 14 dpi, while almost all wheat seedlings were infected by the WT. These results suggested that <em>FpBir1</em> is involved in mycelial morphology, conidial production and germination, and virulence of <em>F</em>. <em>pseudograminearum</em>.</div>
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