Lu Shanfa, Sun Ying-Hsuan, Amerson Henry, Chiang Vincent L
Forest Biotechnology Group, Department of Forestry and Environmental Resources, College of Natural Resources, North Carolina State University, Raleigh, NC 27695, USA.
Plant J. 2007 Sep;51(6):1077-98. doi: 10.1111/j.1365-313X.2007.03208.x. Epub 2007 Jul 17.
MicroRNAs (miRNAs) are endogenous small RNAs that can have large-scale regulatory effects on development and on stress responses in plants. The endemic rust fungus Cronartium quercuum f. sp. fusiforme causes fusiform rust disease in pines, resulting in the development of spindle-shaped galls (cankers) on branches or stems. This disease is the most destructive disease of pines in the southern USA. To test whether miRNAs play roles in fusiform rust gall development, we cloned and identified 26 miRNAs from stem xylem of loblolly pine (Pinus taeda), which belong to four conserved and seven loblolly pine-specific miRNA families. Forty-three targets for nine of these 11 families were experimentally validated in vivo. Sequence analysis suggested that the target cleavage site may be determined not only by the miRNA sequence but also by the target sequence. Members of three loblolly pine-specific miRNA families target a large number of non-protein coding transcripts, and one of these families could also initiate secondary phased production from its target of a putative trans-acting short interfering RNA (ta-siRNA). Expression of 10 of these 11 miRNA families was significantly repressed in the galled stem. PCR-based transcript quantification showed complex expression patterns of these miRNAs and their targets in the galled tissues and in tissues surrounding the gall. We further predict 82 plant disease-related transcripts that may also response to miRNA regulation in pine. These results reveal a new genetic basis for host-pathogen interactions in the development of fusiform rust gall.
微小RNA（miRNA）是一类内源性小RNA，可对植物的发育和应激反应产生大规模的调控作用。地方性锈菌栎柱锈菌梭形专化型（Cronartium quercuum f. sp. fusiforme）可引发松树的梭形锈病，导致树枝或树干上形成纺锤形瘿瘤（溃疡）。这种疾病是美国南部松树最具毁灭性的病害。为了测试miRNA是否在梭形锈病瘿瘤发育中发挥作用，我们从火炬松（Pinus taeda）的茎木质部中克隆并鉴定了26个miRNA，它们属于4个保守的和7个火炬松特异的miRNA家族。在这11个家族中的9个家族的43个靶标在体内得到了实验验证。序列分析表明，靶标切割位点可能不仅由miRNA序列决定，还由靶标序列决定。3个火炬松特异的miRNA家族的成员靶向大量非蛋白质编码转录本，其中一个家族还可从其假定的反式作用短干扰RNA（ta-siRNA）靶标起始次级相位产生。这11个miRNA家族中的10个家族的表达在患病茎中显著受抑制。基于PCR的转录本定量分析显示，这些miRNA及其靶标在患病组织和瘿瘤周围组织中呈现复杂的表达模式。我们进一步预测了82个可能也对松树中miRNA调控有响应的植物病害相关转录本。这些结果揭示了梭形锈病瘿瘤发育过程中宿主-病原体相互作用的新遗传基础。
