Two pathogenesis-related proteins interact with leucine-rich repeat proteins to promote Alternaria leaf spot resistance in apple

Alternaria leaf spot in apple(Malus x domestica),caused by the fungal pathogen Alternaria alternata f.sp.mali(also called A.mali),is a devastating disease resulting in substantial economic losses.We previously established that the resistance(R)protein MdRNL2,containing a coiled-coil,nucleotide-binding,and leucine-rich repeat(CC R-NB-LRR)domain,interacts with another CC R-NB-LRR protein,MdRNL6,to form a MdRNL2–MdRNL6 complex that confers resistance to A.mali.Here,to investigate the function of the MdRNL2–MdRNL6 complex,we identified two novel pathogenesis-related(PR)proteins,MdPR10-1 and MdPR10-2,that interact with MdRNL2.Yeast two-hybrid(Y2H)assays and bimolecular fluorescence complementation(BiFC)assays confirmed that MdPR10-1 and MdPR10-2 interact with MdRNL2 and MdRNL6 at the leucine-rich repeat domain.Transient expression assays demonstrated that accumulation of MdPR10-1 and MdPR10-2 enhanced the resistance of apple to four strains of A.mali that we tested:ALT1,GBYB2,BXSB5,and BXSB7.In vitro antifungal activity assays demonstrated that both the proteins contribute to Alternaria leaf spot resistance by inhibiting fungal growth.Our data provide evidence for a novel regulatory mechanism in which MdRNL2 and MdRNL6 interact with MdPR10-1 and MdPR10-2 to inhibit fungal growth,thereby contributing to Alternaria leaf spot resistance in apple.The identification of these two novel PR proteins will facilitate breeding for fungal disease resistance in apple.

椭圆截面弹体贯穿有限厚金属靶特性研究

本文结合弹性衰减-塑性衰减-开裂三阶段贯穿模型及椭圆截面弹体形状函数,建立了椭圆截面弹体贯穿有限厚金属靶侵彻模型.随后,开展了两种椭圆截面弹体及一种圆截面弹体以230~570 m/s的撞击速度对铝合金靶板的贯穿试验,且试验覆盖了弹道极限速度.在此基础上,采用本文及文献中的试验数据对模型进行了验证,模型的计算结果与试验结果吻合较好.此外,对比分析了椭圆截面弹体与圆截面弹体对有限厚金属靶的贯穿特性.结果表明,当椭圆截面弹体与圆截面弹体的质量、弹体头部长度、任意弹体截面面积及弹体长度相等时,二者可视为等效弹体.其次,确定了无量纲靶体临界厚度与弹体撞击因子间的关系.计算结果表明,无量纲靶体临界厚度与弹体撞击因子呈线性关系,同时,进一步分析了椭圆截面弹体头部形状因子对其贯穿特性的影响规律.