Transcriptome analysis reveals the key role of overdominant expression of photosynthetic and respiration-related genes in the formation of tobacco(Nicotiana tabacum L.) biomass heterosis.

BACKGROUND: Leaves are the nutritional and economic organs of tobacco, and their biomass directly affects tobacco yield and the economic benefits of farmers. In the early stage, our research found that tobacco hybrids have more leaves and larger leaf areas, but the performance and formation reasons of biomass heterosis are not yet clear. RESULTS: This study selected 5 parents with significant differences in tobacco biomass and paired them with hybrid varieties. It was found that tobacco hybrid varieties have a common biomass heterosis, and 45 days after transplantation is the key period for the formation of tobacco biomass heterosis; By analyzing the biomass heterosis of hybrids, Va116×GDH94 and its parents were selected for transcriptome analysis. 76.69% of the differentially expressed genes between Va116×GDH94 and its parents showed overdominant expression pattern, and these overdominant expression genes were significantly enriched in the biological processes of photosynthesis and TCA cycle; During the process of photosynthesis, the overdominant up-regulation of genes such as Lhc, Psa, and rbcl promotes the progress of photosynthesis, thereby increasing the accumulation of tobacco biomass; During the respiratory process, genes such as MDH, ACO, and OGDH are overedominantly down-regulated, inhibiting the TCA cycle and reducing substrate consumption in hybrid offspring; The photosynthetic characteristics of the hybrid and its parents were measured, and the net photosynthetic capacity of the hybrid was significantly higher than that of the parents. CONCLUSION: These results indicate that the overdominant expression effect of differentially expressed genes in Va116×GDH94 and its parents plays a crucial role in the formation of tobacco biomass heterosis. The overdominant expression of genes related to photosynthesis and respiration enhances the photosynthetic ability of Va116×GDH94, reduces respiratory consumption, promotes the increase of biomass, and exhibits obvious heterosis.

Genome-wide identification and characterization of Glutathione S-Transferases (GSTs) and their expression profile under abiotic stresses in tobacco (Nicotiana tabacum L.).

BACKGROUND: Glutathione S-transferases (GSTs) are large and multifunctional proteases that play an important role in detoxification, protection against biotic and abiotic stresses, and secondary metabolite transportation which is essential for plant growth and development. However, there is limited research on the identification and function of NtGSTs. RESULTS: This study uses K326 and other six tobacco varieties (Hongda, HG, GDH11, Va116, VG, and GDH88) as materials to conduct comprehensive genome-wide identification and functional characterization of the GST gene in tobacco. A total of 59 NtGSTs were identified and classified into seven subfamilies via the whole-genome sequence analysis, with the Tau type serving as the major subfamily. The NtGSTs in the same branch of the evolutionary tree had similar exon/intron structure and motif constitution. There were more than 42 collinear blocks between tobacco and pepper, tomato, and potato, indicating high homology conservation between them. Twelve segmental duplicated gene pairs and one tandem duplication may have had a substantial impact on the evolution and expansion of the tobacco GST gene family. The RT-qPCR results showed that the expression patterns of NtGSTs varied significantly among tissues, varieties, and multiple abiotic stresses, suggesting that NtGST genes may widely respond to various abiotic stresses and hormones in tobacco, including NtGSTF4, NtGSTL1, NtGSTZ1, and NtGSTU40. CONCLUSIONS: This study provides a comprehensive analysis of the NtGST gene family, including structures and functions. Many NtGSTs play a critical regulatory role in tobacco growth and development, and responses to abiotic stresses. These findings offer novel and valuable insights for understanding the biological function of NtGSTs and the reference materials for cultivating highly resistant varieties and enhancing the yield and quality of crops.

Negative regulation of tobacco cold stress tolerance by NtPhyA.

Cold stress is a non-biological stressor that adversely affects tobacco yield and leaf quality. Plant photoreceptor proteins, which function as dual light-temperature sensors, play a vital role in temperature changes, making them crucial for responses to non-biological stressors. However, the regulatory mechanisms of PhyA in tobacco remain poorly understood. Therefore, in this study, we aimed to clone the NtPhyA gene from tobacco and generate overexpression (OE-NtPhyA) and mutant (KO-NtPhyA) constructs of NtPhyA. By assessing the physiological and biochemical responses of the mutants under cold stress and performing transcriptome sequencing, we determined the signalling mechanism of NtPhyA under cold stress. Comparative analysis with wild-type (WT) NtPhyA revealed that KO-NtPhyA exhibited increased seed germination rates and reduced wilting under cold stress. In additional, the degree of damage to leaf cells, cell membranes, and stomatal structures was mitigated, and the levels of reactive oxygen species (ROS) were significantly decreased. Antioxidant enzyme activity, net photosynthetic rate, and Fv/Fm were significantly enhanced in KO-NtPhyA, whereas the opposite effects were observed in OE-NtPhyA. These findings indicate that KO-NtPhyA augments tobacco tolerance to cold stress, implying a negative regulatory role of NtPhyA in tobacco during cold stress. Transcriptome analysis revealed that NtPhyA governs the expression of a cascade of genes involved in the response to oxygen-containing compounds, hydrogen peroxide (H2O2), ROS, temperature stimuli, photosystem II oxygen-evolving complex assembly, water channel activity, calcium channel activity, and carbohydrate transport. Collectively, our findings indicate that NtPhyA activates downstream gene expression to enhance the resilience of tobacco to cold stress.