Li Wenqi, Wang Fangquan, Wang Jun, Fan Fangjun, Zhu Jinyan, Yang Jie, Liu Fengquan, Zhong Weigong
Institute of Food Crops, Jiangsu Academy of Agricultural Sciences/Nanjing Branch of Chinese National Center for Rice Improvement/Jiangsu High Quality Rice R&D Center, Nanjing 210014, China.
Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China.
PLoS One. 2015 Mar 18;10(3):e0119867. doi: 10.1371/journal.pone.0119867. eCollection 2015.
The hormone auxin plays an important role not only in the growth and development of rice, but also in its defense responses. We've previously shown that the P450 gene CYP71Z2 enhances disease resistance to pathogens through regulation of phytoalexin biosynthesis in rice, though it remains unclear if auxin is involved in this process or not.
The expression of CYP71Z2 was induced by Xanthomonas oryzae pv. oryzae (Xoo) inoculation was analyzed by qRT-PCR, with GUS histochemical staining showing that CYP71Z2 expression was limited to roots, blades and nodes. Overexpression of CYP71Z2 in rice durably and stably increased resistance to Xoo, though no significant difference in disease resistance was detected between CYP71Z2-RNA interference (RNAi) rice and wild-type. Moreover, IAA concentration was determined using the HPLC/electrospray ionization/tandem mass spectrometry system. The accumulation of IAA was significantly reduced in CYP71Z2-overexpressing rice regardless of whether plants were inoculated or not, whereas it was unaffected in CYP71Z2-RNAi rice. Furthermore, the expression of genes related to IAA, expansin and SA/JA signaling pathways was suppressed in CYP71Z2-overexpressing rice with or without inoculation.
These results suggest that CYP71Z2-mediated resistance to Xoo may be via suppression of IAA signaling in rice. Our studies also provide comprehensive insight into molecular mechanism of resistance to Xoo mediated by IAA in rice. Moreover, an available approach for understanding the P450 gene functions in interaction between rice and pathogens has been provided.
激素生长素不仅在水稻的生长发育中起重要作用，还在其防御反应中发挥作用。我们之前已经表明，P450基因CYP71Z2通过调节水稻中植保素的生物合成来增强对病原体的抗病性，不过生长素是否参与这一过程仍不清楚。
通过qRT-PCR分析了水稻白叶枯病菌（Xoo）接种诱导的CYP71Z2表达，GUS组织化学染色显示CYP71Z2表达仅限于根、叶片和节。在水稻中过表达CYP71Z2可持久稳定地增强对Xoo的抗性，不过在CYP71Z2-RNA干扰（RNAi）水稻和野生型之间未检测到抗病性的显著差异。此外，使用高效液相色谱/电喷雾电离/串联质谱系统测定了吲哚乙酸（IAA）浓度。无论植株是否接种，在过表达CYP71Z2的水稻中IAA的积累均显著减少，而在CYP71Z2-RNAi水稻中IAA积累不受影响。此外，无论是否接种，在过表达CYP71Z2的水稻中，与IAA、扩展蛋白和水杨酸/茉莉酸信号通路相关的基因表达均受到抑制。
这些结果表明，CYP71Z2介导的对Xoo的抗性可能是通过抑制水稻中的IAA信号传导实现的。我们的研究还全面深入地了解了IAA介导的水稻对Xoo抗性的分子机制。此外，还提供了一种了解P450基因在水稻与病原体相互作用中功能的可行方法。
