Interspecific hybridizations with an African tobacco, Nicotiana africana Merxm

2004

Hybrid seedlings from the cross Nicotiana tabacum × N. suaveolens, obtained by test-tube pollination and ovule culture, expressed lethality at 28°C. Characteristic lethal symptoms in these hybrid seedlings consisted of browning of hypocotyls and roots. One hundred and seventeen hybrid seedlings were eventually obtained by the use of test-tube pollination and ovule culture. Hybrid seedlings maintained at 36°C did not express any lethal symptoms. Hybrid seedlings used for further experiments were transferred to 36°C immediately after germination at 28°C. When hybrid seedlings cultured at 36°C were transferred to 28°C, their growth stopped and lethal symptoms were expressed. During the progressive expression of lethality, apoptotic features such as chromatin condensation, nuclear fragmentation and DNA fragmentation were detected. On the other hand, there was no sign of apoptotic cell death in the hybrid seedlings at 36°C. Based on the observation that the same lethal symptoms and the same apoptotic features were observed in the reciprocal cross, N. suaveolens × N. tabacum, we suggest that not only the underlying causes of hybrid lethality but also the underlying causes of apoptotic cell death are due to the interaction of coexisting heterogeneous genomes, rather than to the effect of cytoplasmic genes. Furthermore, the progression of apoptotic cell death in the cross N. tabacum × N. suaveolens began in stems and roots, followed by leaves.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Apoptotic Cell Death Observed during the Expression of Hybrid Lethality in Interspecific Hybrids between Nicotiana tabacum and N. suaveolens

Tezuka

2004

“…In the genus Nicotiana, the hybrid lethality expressed in two interspecific crosses has been studied genetically. Using monosomic analysis, Gerstel et al (1979) suggested that in the cross N. africana × N. tabacum, a gene(s) on the H chromosome of N. tabacum is involved in the expression of lethality in the hybrid seedlings. In the cross N. suaveolens × N. tabacum, the Q chromosome of N. tabacum is responsible for lethality (Marubashi and Onosato 2002).…”

Section: Introductionmentioning

confidence: 99%

Programmed Cell Death Detected in Interspecific Hybrids of Nicotiana repanda * N. tomentosiformis Expressing Hybrid Lethality

Kobori

2004

Interspecific hybrids of Nicotiana repanda × N. tabacum die shortly after germination. Seedlings that are hybrids between N. repanda and N. tomentosiformis, which is a progenitor of N. tabacum, express hybrid lethality when they are cultured at 28°C for 90 days after germination, but seedlings that are hybrids between N. repanda and N. sylvestris, another progenitor of N. tabacum, grow normally. We detected several features of programmed cell death (PCD) in hybrid seedlings of N. repanda × N. tomentosiformis expressing hybrid lethality. Nuclear fragmentation was detected in nuclei isolated from dying shoots and roots of hybrid seedlings expressing lethality. In addition, electrophoresis of total DNA extracted from the shoots and roots of hybrid seedlings showed a distinctive DNA ladder pattern, suggesting cleavage of nuclear DNA into oligonucleosomal fragments. These results indicate that hybrid seedlings of N. repanda × N. tomentosiformis undergo PCD in the process of hybrid lethality. However, in hybrid seedlings of N. repanda × N. sylvestris, no features of PCD were detected. These results suggest that PCD might also be expressed in hybrid seedlings of N. repanda × N. tabacum because N. tomentosiformis is a progenitor of N. tabacum.

“…A gene or genes on the Q chromosome might be related to the process of apoptotic cell death in this cross. Gerstel et al (1979) reported that the H chromosome (from T genome) in N. tabacum was responsible for hybrid lethality between N. tabacum and N. africana. In the cross between N. tabacum and N. suaveolens, the Q chromosome was responsible for hybrid lethality.…”

Section: Discussionmentioning

confidence: 99%

Q Chromosome Controls the Lethality of Interspecific Hybrids between Nicotiana tabacum and N. suaveolens.

Onosato

2002

Non-viable hybrid seedlings were produced from a cross between Nicotiana tabacum (2n = 48; SSTT genome) and N. suaveolens (2n = 32). Our objective was to identify a N. tabacum chromosome that carried gene(s) inducing hybrid lethality in this cross. We crossed 10 monosomic lines (2n = 47; Haplo-M to Z, except for Haplo-p and Haplo-V) of N. tabacum to N. suaveolens and produced hybrids by test-tube pollination and ovule culture using synthetic media. We pollinated 178 placentae (13 to 62 per cross), cultured 5215 ovules (136 to 840 per cross), and produced a total of 85 seedlings. Of the 85 seedlings, 81 died before the cotyledonary and leaf-expansion stages of growth, while 4 from a cross to Haplo-Q produced viable hybrids. Three plants grew to maturity and flowered but one plant was infected by fungi and died at the young stage. Chromosome counting, RAPD and LSC analyses revealed that 3 viable plants were true F 1 hybrids. These results suggested that the Q chromosome of the S genome harbored a gene or genes that induced non-viable seedlings from a cross between N. tabacum and N. suaveolens.