The aquaporin specific control on water versus carbon pathways in leaves is pivotal in controlling gas exchange and leaf hydraulics. We investigated whether Nicotiana tabacum aquaporin 1 (NtAQP1) and ...Nicotiana tabacum plasma membrane intrinsic protein 2; 1 (NtPIP2; 1) gene expression varies in tobacco leaves subjected to treatments with different CO sub(2) concentrations (ranging from 0 to 800 ppm), inducing changes in photosynthesis, stomatal regulation and water evaporation from the leaf. Changes in air CO sub(2) concentration (CO sub(2)) affected net photosynthesis (Pn) and leaf substomatal CO sub(2) (Ci). Pn was slightly negative at 0 ppm air CO sub(2); it was one-third that of ambient controls at 200 ppm, and not different from controls at 800 ppm. Leaves fed with 800 ppm CO sub(2) showed one-third reduced stomatal conductance (g sub(s)) and transpiration (E), and their g sub(s) was in turn slightly lower than in 200 ppm- and in 0 ppm-treated leaves. The 800 ppm air CO sub(2) strongly impaired both NtAQP1 and NtPIP2; 1 gene expression, whereas 0 ppm air CO sub(2), a concentration below any in vivo possible conditions and specifically chosen to maximize the gene expression alteration, increased only the NtAQP1 transcript level. We propose that NtAQP1 expression, an aquaporin devoted to CO sub(2) transport, positively responds to CO sub(2) scarcity in the air in the whole range 0-800 ppm. On the contrary, expression of NtPIP2; 1, an aquaporin not devoted to CO sub(2) transport, is related to water balance in the leaf, and changes in parallel with g sub(s). These observations fit in a model where upregulation of leaf aquaporins is activated at low Ci, while downregulation occurs when high Ci saturates photosynthesis and causes stomatal closure.
Given their critical role in plant reproduction and survival, seeds demand meticulous regulatory mechanisms to effectively store and mobilize reserves. Within seeds, the condition of storage reserves ...heavily depends on environmental stimuli and hormonal activation. Unlike non-protein reserves that commonly employ dedicated regulatory proteins for signaling, proteinaceous reserves may show a unique form of 'self-regulation', amplifying efficiency and precision in this process. Proteins rely on stability to carry out their functions. However, in specific physiological contexts, particularly in seed germination, protein instability becomes essential, fulfilling roles from signaling to regulation. In this study, the elongation factor 1-alpha has been identified as a main proteinaceous reserve in Nicotiana tabacum L. seeds and showed peculiar changes in stability based on tested chemical and physical conditions. A detailed biochemical analysis followed these steps to enhance our understanding of these protein attributes. The protein varied its behavior under different conditions of pH, temperature, and salt concentration, exhibiting shifts within physiological ranges. Notably, distinct solubility transitions were observed, with the elongation factor 1-alpha becoming insoluble upon reaching specific thresholds determined by the tested chemical and physical conditions. The findings are discussed within the context of seed signaling in response to environmental conditions during the key transitions of dormancy and germination.
•In N. tabacum seeds, the elongation factor EF-1α is a main proteinaceous reserve.•The EF-1α serves as environmental sensor for temperature, pH, and salt concentration.•Sensing the environment, the EF-1α has a role in dormancy-to-germination transition.
Increased acidification of the external medium by an activated H super( + ) -ATPase results in cell expansion, in the absence of upstream activating signaling. The plasma membrane H super(+)-ATPase ...couples ATP hydrolysis with proton transport outside the cell, and thus creates an electrochemical gradient, which energizes secondary transporters. According to the acid growth theory, this enzyme is also proposed to play a major role in cell expansion, by acidifying the external medium and so activating enzymes that are involved in cell wall-loosening. However, this theory is still debated. To challenge it, we made use of a plasma membrane H super(+)-ATPase isoform from Nicotiana plumbaginifolia truncated from its C-terminal auto-inhibitory domain ( Delta CPMA4), and thus constitutively activated. This protein was expressed in Nicotiana tabacum BY-2 suspension cells using a heat shock inducible promoter. The characterization of several independent transgenic lines showed that the expression of activated Delta CPMA4 resulted in a reduced external pH by 0.3-1.2 units, as well as in an increased H super(+)-ATPase activity by 77-155 % (ATP hydrolysis), or 70-306 % (proton pumping) of isolated plasma membranes. In addition, Delta CPMA4-expressing cells were 17-57 % larger than the wild-type cells and displayed abnormal shapes. A proteomic comparison of plasma membranes isolated from Delta CPMA4-expressing and wild-type cells revealed the altered abundance of several proteins involved in cell wall synthesis, transport, and signal transduction. In conclusion, the data obtained in this work showed that H super(+)-ATPase activation is sufficient to induce cell expansion and identified possible actors which intervene in this process.
Calmodulin (CaM) is a Ca super(2+)-binding protein that regulates a number of fundamental cellular activities. Nicotiana tabacum CaM (NtCaM) comprises 13 genes classified into three types, among ...which gene expression and target enzyme activation differ. We performed Fourier-transform infrared spectroscopy to compare the secondary and coordination structures of Mg super(2+) and Ca super(2+) among NtCaM1, NtCaM3, and NtCaM13 as representatives of the three types of NtCaMs. Data suggested that NtCaM13 has a different secondary structure due to the weak beta -strand bands and the weak 1661 cm super(-1) band. Coordination structures of Mg super(2+) of NtCaM3 and NtCaM13 were similar but different from that of NtCaM1, while the Ca super(2+)-binding manner was similar among the three CaMs. The amplitude differences of the band at 1554-1550 cm super(-1) obtained by second-derivative spectra indicated that the intensity change of the band of NtCaM13 was smaller in response to Ca super(2+) increases under low Ca super(2+) conditions than were those of NtCaM1 and NtCaM3, while the intensity reached the same level under high Ca super(2+). Therefore, NtCaM13 has a characteristic secondary structure and specific Mg super(2+)-binding manner and needs higher Ca super(2+) for bidentate Ca super(2+) coordination of 12th Glu in EF-hand motifs. The Ca super(2+)-binding mechanisms of the EF-hand motifs of the three CaMs are similar; however, the cation-dependent conformational change in NtCaM13 is unique among the three NtCaMs. copy 2013 Wiley Periodicals, Inc. Biopolymers 99: 472-483, 2013.
To identify genes associated with the cytokinin-induced enhanced drought tolerance, we analyzed the transcriptome of wild-type and transgenic tobacco (Nicotiana tabacum 'SR1') plants expressing ...PSARK::IPT (for senescence-associated receptor kinase::isopentenyltransferase) grown under well-watered and prolonged water deficit conditions using the tomato GeneChip. During water deficit, the expression of genes encoding components of the carotenoid pathway leading to ABA biosynthesis was enhanced in the wild-type plants, but repressed in the transgenic plants. On the other hand, transgenic plants displayed higher transcript abundance of genes involved in the brassinosteroid biosynthetic pathways. Several genes coding for proteins associated with Chl synthesis, light reactions, the Calvin-Benson cycle and photorespiration were induced in the transgenic plants. Notably, increased transcript abundance of genes associated with PSII, the cytochrome b₆/f complex, PSI, NADH oxidoreductase and the ATP complex was found in the PSARK::IPT plants. The increased transcript abundance was assessed by quantitative PCR and the increased protein levels were confirmed by Western blots. Our results indicated that while the photosynthetic apparatus in the wild-type plants was degraded, photosynthesis in the transgenic plants was not affected and photosynthetic proteins were not degraded. During water deficit, wild-type plants displayed a significant reduction in electron transfer and photochemical quenching, with a marked increase in non-photochemical quenching, suggesting a decrease in energy transfer to the PSII core complexes and an increase in cyclic electron transfer reactions.
Seven diterpenes including two new seco-cembranoid basmanoids A (1) and B (2), and two new labdane basmadanes A (3) and B (4), and three known compounds (-)-dehydro-nor-ambreinolid (5), ...(13E)-8-hydroxy-13-labden-12-one (6), and 14,15,16-dinor-7-oxolabda-8-ene-13-oic acid (7) were isolated from oriental tobacco Nicotiana tabacum 'YNOTBS1'. Compounds 1-3 and 5 showed anti-tobacco mosaic virus (TMV) activity with inhibition rates in the range of 30-69% at the concentration of 1 mg/mL. However, none of them exhibited any inhibitory effects against nitric oxide (NO) production in LPS and IFN-γ-induced RAW 264.7 murine macrophages and anti-proliferative activities against cancer cell lines SMMC-7721 and A-549.
Nicotiana tabacum is a kind of plant cultivated for its leaves used for manufacturing medicine and cigarettes. With the common name, the Tobacco plant is grown in many countries including China, ...Indonesia, Malawi and Tanzania just to mention a few. Literatures suggest a technical gap in the proper identification of grade labels for various parts of the plant. In addition, manual grading has resulted in various gaps and biases. To mitigate this, a data-driven grading solution is necessary. However, relevant datasets to train grade classifiers from various countries become of the essence. This article presents images concentrated on tobacco leaf plant position namely Leaf position which normally carries 23 grade labels. Due to high rainfall which swiped away the applied fertilizer on the tobacco plants in the farms, we failed to get images of one grade. Therefore, this research could capture and label 22 grade labels. Images of tobacco leaves based on the tobacco plant position were collected in Tanzania through participatory community research. Canon 5D mark III cameras with 100 mm micro lens were used to take pictures of tobacco leaves based on the tobacco plant position. Domain experts were used for image labelling and cleaning according to tobacco grade labels identified in Tanzania. The dataset carries 49,779 images, which can be used to develop machine learning models for tobacco leaf grade label identification. The collected dataset can be used to train models and enhance the performance of pre-trained models in any country of interest.
Mesophyll conductance significantly, and variably, limits photosynthesis but we currently have no reliable method of measurement for C4 plants.
An online oxygen isotope technique was developed to ...allow quantification of mesophyll conductance in C4 plants and to provide an alternative estimate in C3 plants. The technique is compared to an established carbon isotope method in three C3 species.
Mesophyll conductance of C4 species was similar to that in the C3 species measured, and declined in both C4 and C3 species as leaves aged from fully expanded to senescing. In cotton leaves, simultaneous measurement of carbon and oxygen isotope discrimination allowed the partitioning of total conductance to the chloroplasts into cell wall and plasma membrane versus chloroplast membrane components, if CO2 was assumed to be isotopically equilibrated with cytosolic water, and the partitioning remained stable with leaf age.
The oxygen isotope technique allowed estimation of mesophyll conductance in C4 plants and, when combined with well-established carbon isotope techniques, may provide additional information on mesophyll conductance in C3 plants.
Summary
Melatonin is a multifunctional biomolecule found in both animals and plants. In this review, the biosynthesis, levels, signaling, and possible roles of melatonin and its metabolites in plants ...is summarized. Tryptamine 5‐hydroxylase (T5H), which catalyzes the conversion of tryptamine into serotonin, has been proposed as a target to create a melatonin knockout mutant presenting a lesion‐mimic phenotype in rice. With a reduced anabolic capacity for melatonin biosynthesis and an increased catabolic capacity for melatonin metabolism, all plants generally maintain low melatonin levels. Some plants, including Arabidopsis and Nicotiana tabacum (tobacco), do not possess tryptophan decarboxylase (TDC), the first committed step enzyme required for melatonin biosynthesis. Major melatonin metabolites include cyclic 3‐hydroxymelatonin (3‐OHM) and 2‐hydroxymelatonin (2‐OHM). Other melatonin metabolites such as N1‐acetyl‐N2‐formyl‐5‐methoxykynuramine (AFMK), N‐acetyl‐5‐methoxykynuramine (AMK) and 5‐methoxytryptamine (5‐MT) are also produced when melatonin is applied to Oryza sativa (rice). The signaling pathways of melatonin and its metabolites act via the mitogen‐activated protein kinase (MAPK) cascade, possibly with Cand2 acting as a melatonin receptor, although the integrity of Cand2 remains controversial. Melatonin mediates many important functions in growth stimulation and stress tolerance through its potent antioxidant activity and function in activating the MAPK cascade. The concentration distribution of melatonin metabolites appears to be species specific because corresponding enzymes such as M2H, M3H, catalases, indoleamine 2,3‐dioxygenase (IDO) and N‐acetylserotonin deacetylase (ASDAC) are differentially expressed among plant species and even among different tissues within species. Differential levels of melatonin and its metabolites can lead to differential physiological effects among plants when melatonin is either applied exogenously or overproduced through ectopic overexpression.
Significance Statement
This paper describes melatonin metabolites found in plants and their possible functions as well as their roles as signaling molecules for a series of physiological processes. The representative melatonin metabolites include 2‐hydroxymelatonin (2‐OHM), cyclic 3‐hydroxymelatonin (3‐OHM), and N1‐acetyl‐N2‐formyl‐5‐methoxykynuramine (AFMK).
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