There are more than 80 naturally occurring relatives of cultivated tobacco (Nicotiana tabacum L.) in the genus Nicotiana. In this review, we examine how and to what extent these natural germplasm resources have been utilized in hybridization and introgression experiments over the past century. To date, more than 400 interspecific Nicotiana hybrids have been reported. We focus on individual Nicotiana species involved in interspecific hybrids with cultivated tobacco produced by sexual and asexual methods, including the recently discovered grafting method. Problems related to the hybridization of N. tabacum with other species, namely, cross-incompatibility, maternal phenotypes in hybrid offspring, interspecific incongruity, lethality of juvenile hybrids, and sterility of viable hybrids, are reviewed. Among the 58 interspecific hybrids involving N. tabacum reported thus far, 25 were also reported as somatic hybrids and two were obtained only as somatic hybrids. Thirty-six sterile sexual F1 hybrids were converted to fertile or partly fertile allopolyploids. Sixteen Nicotiana species have been deployed as a source of usable traits that were introgressed into N. tabacum, offering resistance to or tolerance of pathogens or pests. The mechanisms of introgression, such as alien addition and substitution, as well as the barriers and limitations of introgression, including erratic inheritance and adverse linkages, are discussed. Thirty-one Nicotiana species used as sources of cytoplasmic male sterility in N. tabacum have produced multiple alloplasmics; most showed negative effects of alien cytoplasm but a few have been deployed successfully in hybrid cultivars of N. tabacum.

The Use of Nicotiana Species in Tobacco Improvement

Sixteen species of Nicotiana were examined for resistance to second instar larvae of the tobacco horn-worm, Manduca sexta (L.). The tests were designed so as to discriminate between antibiosis and nonpreference. High levels of antibiosis resistance were observed in several wild species such as N. gossei and species in the Repandae section. Several other species, such as N. excelsior, showed antibiosis that appeared to be due to a different mechanism than the alkaloid-trichome exudate based resistance of the above species. The data indicate that these species of Nicotiana may be used as a new source of resistance to larvae of M. sexta.



RESUME

D'especes sauvages de Nicotiania comme nouvelle source de resistance du tabac a Manduca sexta



La resistance aux chenilles de second stade de Manduca sexta L. a ete examinee chez seize especes de Nicotiana. Les essais ont ete concus pour distinguer absence d'appetance et antibiose. Plusieurs especes sauvages comme N. gossei et les especes de la section Repandae ont presente un niveau eleve d'antibiose. D'autres especes, comme N. excelsior ont presente une antibiose vraisemblablement due a un mecanisme different de la resistance des especes precedentes provoquee par un exsudat alcaloide des trichomes. Les resultats indiquent que ces especes de Nicotiana peuvent etre utilisees comme nouvelle source de resistance aux chenilles de M. sexta.

Wild species of Nicotiana as a new source of tobacco resistance to the tobacco hornworm Manduca sexta

The genus Sodalis as a resource for understanding the multifaceted evolution of bacterial symbiosis in insects

ABSTRACT Adaptation of soil microbes due to warming from climate change has been observed, but it remains unknown what microbial growth traits are adaptive to warming. We studied bacterial isolates from the Harvard Forest Long-Term Ecological Research site, where field soils have been experimentally heated to 5°C above ambient temperature with unheated controls for 30 years. We hypothesized that Alphaproteobacteria from warmed plots have (i) less temperature-sensitive growth rates; (ii) higher optimum growth temperatures; and (iii) higher maximum growth temperatures compared to isolates from control plots. We made high-throughput measurements of bacterial growth in liquid cultures over time and across temperatures from 22°C to 37°C in 2–3°C increments. We estimated growth rates by fitting Gompertz models to the growth data. Temperature sensitivity of growth rate, optimum growth temperature, and maximum growth temperature were estimated by the Ratkowsky 1983 model and a modified Macromolecular Rate Theory (MMRT) model. To determine evidence of adaptation, we ran phylogenetic generalized least squares tests on isolates from warmed and control soils. Our results showed evidence of adaptation of higher optimum growth temperature of bacterial isolates from heated soils. However, we observed no evidence of adaptation of temperature sensitivity of growth and maximum growth temperature. Our project begins to capture the shape of the temperature response curves, but illustrates that the relationship between growth and temperature is complex and cannot be limited to a single point in the biokinetic range. IMPORTANCE Soils are the largest terrestrial carbon sink and the foundation of our food, fiber, and fuel systems. Healthy soils are carbon sinks, storing more carbon than they release. This reduces the amount of carbon dioxide released into the atmosphere and buffers against climate change. Soil microbes drive biogeochemical cycling and contribute to soil health through organic matter breakdown, plant growth promotion, and nutrient distribution. In this study, we determined how soil microbial growth traits respond to long-term soil warming. We found that bacterial isolates from warmed plots showed evidence of adaptation of optimum growth temperature. This suggests that increased microbial biomass and growth in a warming world could result in greater carbon storage. As temperatures increase, greater microbial activity may help reduce the soil carbon feedback loop. Our results provide insight on how atmospheric carbon cycling and soil health may respond in a warming world. 

Thermal adaptation of soil microbial growth traits in response to chronic warming

Fiber film have received widespread attention due to its green friendliness. We can use microorganisms to degrade lignin in straw to obtain cellulose and make fiber films. Herein, a group of high-temperature (50 °C) lignin degrading bacterial consortium (LDH) was enriched and culture conditions for lignin degradation were optimized. Combined with high-throughput sequencing technology, the synergistic effect of LDH-composited bacteria was analyzed. Then LDH was used to treat rice straw for the bio-pulping experiment. The results showed that the lignin of rice straw was degraded 32.4 % by LDH at 50 °C for 10 d, and after the optimization of culture conditions, lignin degradation rate increased by 9.05 % (P < 0.001). The bacteria that compose in LDH can synergistically degrade lignin. Paenibacillus can encode all lignin-degrading enzymes present in the LDH. Preliminary tests of LDH in the pulping industry have been completed. This study is the first to use high temperature lignin degrading bacteria to fabricate fiber film. 

Synergistic analysis of lignin degrading bacterial consortium and its application in rice straw fiber film.

In tobacco (Nicotiana tabacum L.), there is a very little scope for intervarietal gene transfer, hence interspecific hybridization utilising wild species of the genus Nicotiana possessing resistance to one or more pests, is the best solution. Eventhough N. benthamiana is resistant to tobacco caterpillar (Spodoptera litura F.), in view of its interspecific incompatibility with N. tabacum, a trispecific amphiploid (N. benthamiana×N. glutinosa×N. tabacum) was synthesised with N. glutinosa as a bridge species. Progressive elimination of N. benthamiana and N. glutinosa chromosomes was achieved through four successive back-crosses of the amphiploid with flue-cured N. tabacum varieties, resulting in plants having most of the tabacum characters and caterpillar resistance. All the plants were male-sterile and most of them possessed 48-50 mitotic chromosomes, 48 from N. tabacum and 1-2 from N. bentamiana thus indicating that the resistance factors are confined to one or two chromosomes. Based on the mortality of inoculated larvae and the extent of damage, the plants were grouped into highly resistant, moderately resistant and susceptible types.The heavy mortality of the caterpillar within 24 hours indicate that certain toxic exudates from the leaf surface may be the primary cause of death. Starvation due to “non-preference” may be another factor responsible for death of most of the remaining larvae within the next 24-240 hours. The retarded growth of a few surviving larvae, their resistant feeding and the slow pace at which they proceed from one instar to another indicate that some “antibiosis” properties may also be associated with the factors for resistance.

Interspecific Transfer of Resistance to Tobacco Caterpillar (Spodoptera litura F.) from N. benthamiana to N. tabacum.

Below-ground carbon transformations represent a natural climate change mitigation solution, but newly-acquired traits adaptive to climate stress may alter microbial climate feedback mechanisms. To better define microbial evolutionary responses to long-term climate warming, we study microorganisms from an ongoing in situ soil warming experiment at the Harvard Forest Long-term Ecological Research (LTER) site where, for over three decades, soils are continuously heated 5 °C above ambient temperatures. We hypothesize that across generations of chronic warming, genomic signatures within diverse bacterial lineages reflect trait-based adaptations related to growth and carbon utilization. From our culture collection of soil bacteria isolated from experimental heated and control plots, we sequenced genomes representing taxa dominant in soil communities and sensitive to warming, including independent lineages of Alphaproteobacteria, Actinobacteria, and Betaproteobacteria. We investigated differences in genomic attributes and patterns of functional gene content to identify genetic signatures of adaptation. Comparative pangenomics revealed differently abundant gene clusters with functional annotations related to carbon and nitrogen metabolism. We also observed differences in global codon usage bias between heated and control genomes, suggesting potential adaptive traits related to growth or growth efficiency. This effect was more varied for organisms with fewer 16S rrn operons, suggesting that these organisms experience different selective pressures on growth efficiency. Together, these data illustrate the emergence of lineage-specific traits as well as common ecological-evolutionary microbial responses to climate change.

/pdf/pangenomes-reveal-genomic-signatures-of-microbial-adaptation-2boqtc4v.pdf

Pangenomes reveal genomic signatures of microbial adaptation to experimental soil warming

Adaptation of soil microbes due to warming from climate change has been observed, but it remains unknown what microbial growth traits are adaptive to warming. We studied bacterial isolates from the Harvard Forest Long-Term Ecological Research site, where field soils have been experimentally heated to 5°C above ambient temperature with unheated controls for thirty years. We hypothesized that Alphaproteobacteria from warmed plots have (1) less temperature sensitive growth rates; (2) higher optimum growth temperatures; and (3) higher maximum growth temperatures compared to isolates from control plots. We made high-throughput measurements of bacterial growth in liquid cultures over time and across temperatures from 22-37°C in 2-3°C increments. We estimated growth rates by fitting Gompertz models to the growth data. Temperature sensitivity of growth rate, optimum growth temperature, and maximum growth temperature were estimated by the Ratkowsky 1983 model and a modified Macromolecular Rate Theory (MMRT) model. To determine evidence of adaptation, we ran phylogenetic generalized least squares tests on isolates from warmed and control soils. Our results showed evidence of adaptation of higher optimum growth temperature of bacterial isolates from heated soils. However, we observed no evidence of adaptation of temperature sensitivity of growth and maximum growth temperature. Our project begins to capture the shape of the temperature response curves, but illustrates that the relationship between growth and temperature is complex and cannot be limited to a single point in the biokinetic range. Importance Soils are the largest terrestrial carbon sink and the foundation of our food, fiber, and fuel systems. Healthy soils are carbon sinks, storing more carbon than they release. This reduces the amount of carbon dioxide released to the atmosphere and buffers against climate change. Soil microbes drive biogeochemical cycling and contribute to soil health through organic matter breakdown, plant growth promotion, and nutrient distribution. In this study, we determined how soil microbial growth traits respond to long-term soil warming. We found that bacterial isolates from warmed plots showed evidence of adaptation of increased optimum growth temperature. This suggests that increased microbial biomass and growth relative to respiration in a warming world should result in greater carbon storage. As temperatures increase, greater microbial activity may help reduce the soil carbon feedback loop. Our results provide insight on how atmospheric carbon cycling and soil health may respond in a warming world.

https://www.biorxiv.org/content/biorxiv/early/2023/05/20/2023.05.19.541531.full.pdf

Currently, in the paper industry, paper mill pulping relies on unsustainable and costly processes to remove lignin from lignocellulosic material. A greener approach is biopulping, which uses microbes and their enzymes to break down lignin. ABSTRACT Novel bacterial isolates with the capabilities of lignin depolymerization, catabolism, or both, could be pertinent to lignocellulosic biofuel applications. In this study, we aimed to identify anaerobic bacteria that could address the economic challenges faced with microbial-mediated biotechnologies, such as the need for aeration and mixing. Using a consortium seeded from temperate forest soil and enriched under anoxic conditions with organosolv lignin as the sole carbon source, we successfully isolated a novel bacterium, designated 159R. Based on the 16S rRNA gene, the isolate belongs to the genus Sodalis in the family Bruguierivoracaceae. Whole-genome sequencing revealed a genome size of 6.38 Mbp and a GC content of 55 mol%. To resolve the phylogenetic position of 159R, its phylogeny was reconstructed using (i) 16S rRNA genes of its closest relatives, (ii) multilocus sequence analysis (MLSA) of 100 genes, (iii) 49 clusters of orthologous groups (COG) domains, and (iv) 400 conserved proteins. Isolate 159R was closely related to the deadwood associated Sodalis guild rather than the tsetse fly and other insect endosymbiont guilds. Estimated genome-sequence-based digital DNA-DNA hybridization (dDDH), genome percentage of conserved proteins (POCP), and an alignment analysis between 159R and the Sodalis clade species further supported that isolate 159R was part of the Sodalis genus and a strain of Sodalis ligni. We proposed the name Sodalis ligni str. 159R (=DSM 110549 = ATCC TSD-177). IMPORTANCE Currently, in the paper industry, paper mill pulping relies on unsustainable and costly processes to remove lignin from lignocellulosic material. A greener approach is biopulping, which uses microbes and their enzymes to break down lignin. However, there are limitations to biopulping that prevent it from outcompeting other pulping processes, such as requiring constant aeration and mixing. Anaerobic bacteria are a promising alternative source for consolidated depolymerization of lignin and its conversion to valuable by-products. We presented Sodalis ligni str. 159R and its characteristics as another example of potential mechanisms that can be developed for lignocellulosic applications.

Sodalis ligni Strain 159R Isolated from an Anaerobic Lignin-Degrading Consortium

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Interspecific Transfer of Resistance to Tobacco Caterpillar (Spodoptera litura F.) from N. benthamiana to N. tabacum.

Pangenomes reveal genomic signatures of microbial adaptation to experimental soil warming

Thermal adaptation of soil microbial growth traits in response to chronic warming

Sodalis ligni Strain 159R Isolated from an Anaerobic Lignin-Degrading Consortium