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

Abstract

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.

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

“…Recently, hybrid lethality has been expressed in several interspecific crosses, such as N. glutinosa × N. repanda (Marubashi et al 1999), N. suaveolens × N. tabacum (Yamada et al 2000), N. debneyi × N. tabacum Kobayashi 2002a, 2002b), N. tabacum × N. suaveolens (Tezuka and Marubashi 2004), and N. langsdorffii × N. tabacum (Watanabe and Marubashi 2004). In addition, features of PCD (or apoptotic cell death), including nuclear fragmentation and cleavage of nuclear DNA into oligonucleosomal fragments, which are considered the key characteristics of PCD in plant cells undergoing a hypersensitive response (Ryerson andHeath 1996, Wang et al 1996), were observed during hybrid lethality.…”

“…In addition, features of PCD (or apoptotic cell death), including nuclear fragmentation and cleavage of nuclear DNA into oligonucleosomal fragments, which are considered the key characteristics of PCD in plant cells undergoing a hypersensitive response (Ryerson andHeath 1996, Wang et al 1996), were observed during hybrid lethality. Cytometric analysis and agarose gel electrophoresis are generally applied as diagnostic tools for PCD in plant cells during expression of hybrid lethality (Marubashi et al 1999, Yamada et al 2000, Marubashi and Kobayashi 2002a, 2002b, Tezuka and Marubashi 2004, Watanabe and Marubashi 2004. N. repanda Willd.…”

Hybrid lethality with programmed cell death results from reciprocal interspecific crosses between Nicotiana nudicaulis Watson and N. tabacum L.

“…Hybrid seedlings from reciprocal interspecific crosses between N. suaveolens (section Suaveolentes) and N. tabacum express lethality (Manabe et al 1989;Tezuka and Marubashi 2004), which is accompanied by programmed cell death (PCD) (Tezuka and Marubashi 2004;Yamada et al 2000). Furthermore, the Q chromosome belonging to the S subgenome of N. tabacum (SSTT) is responsible for this hybrid lethality (Inoue et al 1996;Marubashi and Onosato 2002).…”

“…tabacum also express lethality and PCD accompanies this lethality (Marubashi and Kobayashi 2002;Tezuka et al 2006). This hybrid lethality was controlled by the interaction between a single dominant gene, Hybrid Lethality A1 (HLA1), in N. debneyi and gene(s) on the Q chromosome in N. tabacum (Iizuka et al 2011;Tezuka et al 2007).…”

Characterization of hybrid seedlings from crosses of <i>Nicotiana stocktonii</i> Brandegee×<i>N. tabacum</i> L. and <i>N. stocktonii</i>×progenitors of <i>N. tabacum</i>

“…tabacum develop browning at the hypocotyl and die at the cotyledonary stage via apoptotic cell death (Yamada et al 2000). The same lethal symptoms are observed in hybrids derived from the reciprocal cross through test-tube pollination and ovule culture (Tezuka and Marubashi 2004). N. tabacum is a natural amphidiploid (2n=48, SSTT), which presumably originated by interspecific hybridization of N. sylvestris (2n=24, SS) with N. tomentosiformis (2n=24, TT) and subsequent chromosome doubling (Gray et al 1974;Murad et al 2002;Sheen 1972).…”