Phenylalanine ammonia-lyase and phenolic compounds are related to hybrid lethality in the cross <i>Nicotiana suaveolens</i>×<i>N. tabacum</i>

Abstract

Hybrid lethality observed in hybrid seedlings between Nicotiana suaveolens and N. tabacum is characterized by browning, initially of the hypocotyls and eventually of entire seedlings. We investigated the mechanism underlying this browning of tissues. A phenylalanine ammonia-lyase (PAL) gene codes an enzyme involved in a pathway producing phenolic compounds related to the browning of plant tissues. The expression of PAL rapidly increased with the induction of hybrid lethality. Phenolic compounds were observed to be accumulated in whole parts of hybrid seedlings. Treatment of hybrid seedlings with L-2-aminooxy-3-phenylpropionic acid (AOPP), an inhibitor for PAL, suppressed browning and decreased the phenolic content of hybrid seedlings. Although programmed cell death (PCD) was involved in hybrid lethality, AOPP treatment also suppressed cell death and enhanced the growth of hybrid seedlings. These results indicated that PAL is involved in hybrid lethality, and phenolic compounds could be the cause of hybrid lethality-associated tissue browning.

Analysis of the possible cytogenetic mechanism for overcoming hybrid lethality in an interspecific cross between Nicotiana suaveolens and Nicotiana tabacum

“…Hybrid lethality has been demonstrated in various combinations of interspecific crosses in the genus Nicotiana 4 . Hybrid seedlings of Nicotiana suaveolens (2n = 2 × = 32, genome constitution SuSu) and N. tabacum (2n = 4 × = 48, SSTT, the S genome is derived from N. sylvestris , and the T genome is derived from N. tomentosiformis 5 ) germinate normally, but show type-II lethality, with the hypocotyl turning brown and dying several days after germination (DAG) 6 . It has been reported that the amount of transcript of PAL , an immune response-related gene that encodes phenylalanine ammonia-lyase, is increased in hybrid seedlings that show lethality 6 .…”

“…Hybrid seedlings of Nicotiana suaveolens (2n = 2 × = 32, genome constitution SuSu) and N. tabacum (2n = 4 × = 48, SSTT, the S genome is derived from N. sylvestris , and the T genome is derived from N. tomentosiformis 5 ) germinate normally, but show type-II lethality, with the hypocotyl turning brown and dying several days after germination (DAG) 6 . It has been reported that the amount of transcript of PAL , an immune response-related gene that encodes phenylalanine ammonia-lyase, is increased in hybrid seedlings that show lethality 6 . We also have confirmed that the accumulation of protein aggregates promotes programmed cell death via autophagy in cultured cells of N. suaveolens × N. tabacum hybrids that exhibit lethality 7 , 8 .…”

Genetic Mapping of the HLA1 Locus Causing Hybrid Lethality in Nicotiana Interspecific Hybrids

“…Considering that some types of disease resistance responses are temperature sensitive [27][28][29] and involve programmed cell death [30], the results from the experiments on hybrid lethality in Nicotiana have suggested that disease resistance-related responses might be associated with hybrid lethality. Several genes and proteins also relevant to disease resistance have been identified in the process of hybrid lethality [31][32][33][34]. However, the causal genes for hybrid lethality in Nicotiana are poorly understood.…”

Overcoming Hybrid Lethality Induced by Chromosomal Instability in an Interspecific Hybrid of Genus Nicotiana

“…It is known that hybrid lethality also occurs in various combinations of interspeci c crosses in the genus Nicotiana 4 . Hybrid seedlings of Nicotianasuaveolens (2n = 2x = 32, genome constitution SuSu) and Nicotianatabacum (2n = 4x = 48, SSTT) germinate normally, but show type-II lethality, such that the hypocotyl browns and eventually dies a few days after germination (DAG) 5 . It has been reported that the amount of transcript of PAL (encoding phenylalanine ammonia-lyase), which is an immune responserelated gene, is increased in hybrid seedlings that show lethality 5 .…”

“…Hybrid seedlings of Nicotianasuaveolens (2n = 2x = 32, genome constitution SuSu) and Nicotianatabacum (2n = 4x = 48, SSTT) germinate normally, but show type-II lethality, such that the hypocotyl browns and eventually dies a few days after germination (DAG) 5 . It has been reported that the amount of transcript of PAL (encoding phenylalanine ammonia-lyase), which is an immune responserelated gene, is increased in hybrid seedlings that show lethality 5 . We also have con rmed that the accumulation of protein aggregates promotes programmed cell death via autophagy in cultured cells of N.suaveolens x N.tabacum hybrids that exhibit lethality 6,7 .…”