Nuclear Transition Between the Conjunction Cells of Phaeodactylum tricornutum Bohlin (Bacillariophyta)

Phaeodactylum tricornutum is one of the important marine diatoms for oceanic primary production. Its reproduction has profound significance in the life cycle; however, the nuclear behavior during its sexual reproduction was not clear. In this study, we observed the nuclear transition and determined its correlation with cell conjunction. It was found that two cells jointed at their apices first and swung and aligned each other immediately, and nucleus from one cell was able to transfer into another one during cell conjugation. The cell pairs conjugated for nuclear transition were different from those formed in mitosis in hypovalve thickness and cellular arrangement. Our findings proved the existence of sexual reproduction in P. tricornutum.

依据减数分裂特异基因判定三角褐指藻生殖方式的研究

生殖方式既是重要的生物学特征,也关乎遗传改良策略的选择。在三角褐指藻(Phaeodactylun tricornutum)中,真核生物中广泛存在的有性生殖过程从未被观察到。除直接观察有性生殖过程和依据遗传后果判定,还可根据减数分裂特异基因存在与否判定是否存在有性生殖。在三角褐指藻基因组序列中搜索减数分裂特异基因,用ClustalX进行序列比,用Mrbaye3.2软件构建分子系统学树,进行分子系统学分析,发现三角褐指藻缺失7个减数分裂特异基因中的3个,分别是Hop1,Mnd1和Dmc1。不能观察到有性生殖时,绝大多数(或全部)减数分裂特异基因存在可佐证有性生殖存在,而这些基因缺失则意味着减数分裂丧失和专营无性生殖。因三角褐指藻缺失部分减数分裂特异基因,故推论其专营无性生殖。无性生殖可维持遗传稳定,研究结果有助于通过选择优良藻株培育三角褐指藻的优良品种。