Hybrid lethality in interspecific hybrids between Nicotiana tabacum and N. suaveolens: evidence that the Q chromosome causes hybrid lethality based on Q-chromosome-specific DNA markers

Abstract

Hybrid seedlings from the cross Nicotiana tabacum x N. suaveolens express lethality at 28 degrees C. We carried out a cross between monosomic lines of N. tabacum lacking the Q chromosome and N. suaveolens by test-tube pollination and ovule culture at 28 degrees C. To suppress hybrid lethality, hybrid seedlings obtained were transferred to 36 degrees C immediately after germination and cultured. We determined whether Q-chromosome-specific DNA markers were detected among hybrid seedlings. When hybrid seedlings cultured at 36 degrees C were transferred to 28 degrees C, hybrid seedlings in which Q-chromosome-specific DNA markers were detected expressed hybrid lethality, while hybrid seedlings in which Q-chromosome-specific DNA markers were not detected did not express hybrid lethality. From these results, we concluded that the presence of the Q chromosome of N. tabacum is related to hybrid lethality observed in crosses between N. tabacum and N. suaveolens. This is the first report that clearly demonstrates the relationship between a certain chromosome and hybrid lethality in the genus Nicotiana using chromosome-specific DNA markers. Additionally, we confirmed that the Q chromosome belongs to the S subgenome because Q-chromosome-specific DNA markers were detected only in N. sylvestris.

Possible involvement of genes on the Q chromosome of Nicotiana tabacum in expression of hybrid lethality and programmed cell death during interspecific hybridization to Nicotiana debneyi

“…Two Q-chromosome-speciWc DNA markers, QCS2 and QCS3, were detected as previously described Tezuka and Marubashi 2006b). …”

Identification of genomic factors responsible for hybrid lethality in hybrids between Nicotiana nudicaulis Watson and N. tabacum L.

“…Only when Haplo-Q was crossed with N. suaveolens could viable plants be obtained. Furthermore, when Haplo-Q is crossed with N. suaveolens and the hybrid seedlings cultured at 36°C are transferred to 28°C, those possessing the Q chromosome die and those lacking the Q chromosome do not (Tezuka and Marubashi 2006). In the present study, hybrid seedlings both possessing and lacking the Q chromosome died within 10 days of transfer from 34 to 28°C.…”

“…PCR products were separated by electrophoresis on 1.5% agarose gels in TAE buffer and stained with ethidium bromide to visualize DNA bands. The Q-chromosome-specific DNA marker QCS1 was detected as described by Tezuka and Marubashi (2006).…”

“…In these hybrids, the number of monosomic plants was almost the same as disomic plants. Using this approach, Tezuka et al (2006) carried out crosses of Haplo-Q×N. suaveolens and found by using four Q-chromosomespecific DNA markers that hybrid seedlings in which Q-chromosome-specific DNA markers were detected expressed hybrid lethality, while hybrid seedlings in which Q-chromosome-specific DNA markers were not detected did not.…”

Searching for genetic factors involved in hybrid lethality in Nicotiana; Possible use of a cultured cell line of a hybrid

“…This provides for another possibility, that the inhibition of cell death was not directly due to an absence of E2 per se from the genome of GTH4S, but rather, caused by the deletion of the neighboring region of the chromosome around this locus. Tezuka and Marubashi (2006) suggested that the Qchromosome which belongs to the S subgenome in N. tabacum was a counterpart for the expression of lethality in the hybrid of N. tabacumϫN. suaveolens.…”