Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Sakai, Osaka, Japan.
PLoS One. 2012;7(4):e36204. doi: 10.1371/journal.pone.0036204. Epub 2012 Apr 26.
Many species of Nicotiana section Suaveolentes produce inviable F(1) hybrids after crossing with Nicotiana tabacum (genome constitution SSTT), a phenomenon that is often called hybrid lethality. Through crosses with monosomic lines of N. tabacum lacking a Q chromosome, we previously determined that hybrid lethality is caused by interaction between gene(s) on the Q chromosome belonging to the S subgenome of N. tabacum and gene(s) in Suaveolentes species. Here, we examined if hybrid seedlings from the cross N. occidentalis (section Suaveolentes)×N. tabacum are inviable despite a lack of the Q chromosome.
METHODOLOGY/PRINCIPAL FINDINGS: Hybrid lethality in the cross of N. occidentalis×N. tabacum was characterized by shoots with fading color. This symptom differed from what has been previously observed in lethal crosses between many species in section Suaveolentes and N. tabacum. In crosses of monosomic N. tabacum plants lacking the Q chromosome with N. occidentalis, hybrid lethality was observed in hybrid seedlings either lacking or possessing the Q chromosome. N. occidentalis was then crossed with two progenitors of N. tabacum, N. sylvestris (SS) and N. tomentosiformis (TT), to reveal which subgenome of N. tabacum contains gene(s) responsible for hybrid lethality. Hybrid seedlings from the crosses N. occidentalis×N. tomentosiformis and N. occidentalis×N. sylvestris were inviable.
CONCLUSIONS/SIGNIFICANCE: Although the specific symptoms of hybrid lethality in the cross N. occidentalis×N. tabacum were similar to those appearing in hybrids from the cross N. occidentalis×N. tomentosiformis, genes in both the S and T subgenomes of N. tabacum appear responsible for hybrid lethality in crosses with N. occidentalis.
许多茄科烟草亚族的Nicotiana 种与烟草（基因组构成为 SSTT）杂交后会产生不可育的 F(1)杂种，这种现象通常称为杂种致死性。通过与缺乏 Q 染色体的烟草单体系杂交，我们之前确定杂种致死性是由烟草 S 亚基因组 Q 染色体上的基因与茄科烟草亚族物种中的基因之间的相互作用引起的。在这里，我们检查了来自 Nicotiana occidentalis（茄科烟草亚族）×烟草的杂种幼苗是否在缺乏 Q 染色体的情况下是不可育的。
方法/主要发现：Nicotiana occidentalis×烟草杂交的杂种致死性表现为茎色褪绿。这种症状与之前在茄科烟草亚族的许多物种与烟草之间的致死性杂交中观察到的不同。在缺乏 Q 染色体的烟草单体系植物与 Nicotiana occidentalis 的杂交中，观察到杂种致死性在缺乏或存在 Q 染色体的杂种幼苗中。然后，将 Nicotiana occidentalis 与烟草的两个祖先 N. sylvestris（SS）和 N. tomentosiformis（TT）杂交，以揭示烟草的哪个亚基因组包含负责杂种致死性的基因。来自 Nicotiana occidentalis×N. tomentosiformis 和 Nicotiana occidentalis×N. sylvestris 的杂种幼苗是不可育的。
结论/意义：尽管 Nicotiana occidentalis×烟草杂交中的杂种致死性的具体症状与 Nicotiana occidentalis×N. tomentosiformis 杂交中的杂种相似，但烟草的 S 和 T 亚基因组中的基因似乎都负责与 Nicotiana occidentalis 杂交的杂种致死性。
