Costa José-Luis, Romero Esperanza Martínez, Lindblad Peter
Department of Physiological Botany, Uppsala University, Villavägen 6, SE-752 36 Uppsala, Sweden.
FEMS Microbiol Ecol. 2004 Sep 1;49(3):481-7. doi: 10.1016/j.femsec.2004.05.001.
The genetic diversity of cyanobacteria associated with cycads was examined using the tRNA(Leu) (UAA) intron as a genetic marker. Coralloid roots of both natural populations of the cycad Macrozamia riedlei (Fischer ex Gaudichaud-Beaupré) C.A. Gardner growing in Perth, Australia and cycads growing in greenhouses, also in Perth, were used and their respective cyanobionts analyzed. Several Nostoc strains were found to be involved in this symbiosis, both in natural populations and greenhouse-originated cycads. However, only one strain was present in individual coralloid roots and in individual plants, even when analyzing different coralloid roots from the same plant. Moreover, when examining plants growing close to each other (female plants and their respective offspring) the same cyanobacterium was consistently present in the different coralloid roots. Whether this reflects a selective mechanisms or merely the availability of Nostoc strains remains to be ascertained. The high cyanobacterial diversity in coralloid roots of cycads revealed by PCR fingerprinting is, therefore, contested. In this study, the potential problems of using different methods (e.g., PCR fingerprinting) to study the genetic diversity of symbiotic cyanobacteria, is also addressed.
利用tRNA(Leu)(UAA)内含子作为遗传标记，对与苏铁相关的蓝细菌的遗传多样性进行了研究。使用了生长在澳大利亚珀斯的苏铁大泽米（Macrozamia riedlei (Fischer ex Gaudichaud-Beaupré) C.A. Gardner）自然种群的珊瑚状根，以及同样生长在珀斯温室中的苏铁的珊瑚状根，并对它们各自的共生蓝细菌进行了分析。在自然种群和温室来源的苏铁中，均发现有几种念珠藻菌株参与了这种共生关系。然而，即使分析同一植株的不同珊瑚状根，在单个珊瑚状根和单个植株中也仅存在一种菌株。此外，在检查彼此相邻生长的植株（雌株及其各自的后代）时，不同的珊瑚状根中始终存在相同的蓝细菌。这是反映了一种选择机制，还是仅仅是念珠藻菌株的可获得性，仍有待确定。因此，PCR指纹图谱揭示的苏铁珊瑚状根中蓝细菌的高多样性受到了质疑。在本研究中，还讨论了使用不同方法（如PCR指纹图谱）研究共生蓝细菌遗传多样性时可能存在的问题。
