Molecular insights into the functional role of nitric oxide (NO) as a signal for plant responses in chickpea

The molecular mechanisms and targets of nitric oxide (NO) are not fully known in plants. Our study reports the first large-scale quantitative proteomic analysis of NO donor responsive proteins in chickpea. Dose response studies carried out using NO donors, sodium nitroprusside (SNP), diethylamine NONOate (DETA) and S-nitrosoglutathione (GSNO) in chickpea genotype ICCV1882, revealed a dose dependent positive impact on seed germination and seedling growth. SNP at 0.1 mM concentration proved to be most appropriate following confirmation using four different chickpea genotypes. while SNP treatment enhanced the percentage of germination, chlorophyll and nitrogen contents in chickpea, addition of NO scavenger, cPTIO reverted its impact under abiotic stresses. Proteome profiling revealed 172 downregulated and 76 upregulated proteins, of which majority were involved in metabolic processes (118) by virtue of their catalytic (145) and binding (106) activity. A few crucial proteins such as S-adenosylmethionine synthase, dehydroascorbate reductase, pyruvate kinase fragment, 1-aminocyclopropane-1-carboxylic acid oxidase, 1-pyrroline-5-carboxylate synthetase were less abundant whereas Bowman-Birk type protease inhibitor, non-specific lipid transfer protein, chalcone synthase, ribulose-1-5-bisphosphate carboxylase oxygenase large subunit, PSII D2 protein were highly abundant in SNP treated samples. This study highlights the protein networks for a better understanding of possible NO induced regulatory mechanisms in plants

NO to drought-multifunctional role of nitric oxide in plant drought: Do we have all the answers?

Nitric oxide (NO) is a versatile gaseous signaling molecule with increasing significance in plant research due to its association with various stress responses. Although, improved drought tolerance by NO is associated greatly with its ability to reduce stomatal opening and oxidative stress, it can immensely influence other physiological processes such as photosynthesis, proline accumulation and seed germination under water deficit. NO as a free radical can directly alter proteins, enzyme activities, gene transcription, and post-translational modifications that benefit functional recovery from drought. The present drought-mitigating strategies have focused on exogenous application of NO donors for exploring the associated physiological and molecular events, transgenic and mutant studies, but are inadequate. Considering the biphasic effects of NO, a cautious deployment is necessary along with a systematic approach for deciphering positively regulated responses to avoid any cytotoxic effects. Identification of NO target molecules and in-depth analysis of its effects under realistic field drought conditions should be an upmost priority. This detailed synthesis on the role of NO offers new insights on its functions, signaling, regulation, interactions and co-existence with different drought-related events providing future directions for exploiting this molecule towards improving drought tolerance in crop plants

Heat induced differential proteomic changes reveal molecular mechanisms responsible for heat tolerance in chickpea

Understanding the molecular differences in plant genotypes contrasting for heat sensitivity can provide useful insights into the mechanisms that confer heat tolerance in plants. We focused on comparative physiological and proteomic analyses of heat sensitive (ICC16374) and tolerant (JG14) genotypes of chickpea (Cicer arietinum L.) when subjected to heat stress at anthesis. Heat stress reduced seed germination, leaf water content, chlorophyll content and membrane integrity with a greater impact on sensitive genotype than on the tolerant ones that had higher total antioxidant capacity and osmolyte accumulation, and consequently less oxidative damage. Comparative gel-free proteome profiles indicated differences in the expression levels and regulation of common proteins that are associated with heat tolerance in contrasting genotypes under heat stress. Several crucial heat induced and heat responsive proteins were identified and categorized based on ontology and pathway analysis. The proteins which are essentially related to the electron transport chain in photosynthesis, aminoacid biosynthesis, ribosome synthesis and secondary metabolite synthesis may play key roles in inducing heat tolerance. In addition, our study also provides evidence that the foliar application of nitric oxide (NO) donor can enhance heat and drought stress tolerance by modulating a number of proteins in chickpea. Understanding the active metabolic adjustments in tolerant genotype under stress and inducing the stress tolerance in sensitive genotype by exogenous NO application offers a comprehensive and systematic approach to tackle heat and drought stress in chickpea. This study potentially contributes to improved stress resilience by offering valuable insights on the mechanisms of heat and drought tolerance in chickpea

Heat responsive proteome changes reveal molecular mechanisms underlying heat tolerance in chickpea

Understanding the molecular differences in plant genotypes contrasting for heat sensitivity can provide useful insights into the mechanisms that confer heat tolerance in plants. This study focuses on comparative physiological and proteomic analyses of heat-sensitive (ICC16374) and heat-tolerant (JG14) genotypes of chickpea (Cicer arietinum L.) under heat stress impositions at anthesis. Heat stress reduced leaf water content, chlorophyll content and membrane integrity with a greater impact on the sensitive genotype compared to the tolerant one that had higher total antioxidant capacity and osmolyte accumulation, and consequently less oxidative damage. This study identified a set of 482 heat-responsive proteins in the tolerant genotype using comparative gel-free proteomics. Besides heat shock proteins, proteins such as acetyl-CoA carboxylase, pyrroline-5-carboxylate synthase (P5CS), ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO), phenylalanine ammonia-lyase (PAL) 2, ATP synthase, glycosyltransferase, sucrose synthase and late embryogenesis abundant (LEA) proteins were strongly associated with heat tolerance in chickpea. Several crucial proteins were induced by heat exclusively in the heat-tolerant genotype. Comparative proteome profiling and pathway analysis revealed mitigating strategies including, accumulation of osmoprotectants, protected membrane transport, ribosome and secondary metabolite synthesis, activation of antioxidant and defense compounds, amino acid biosynthesis, and hormonal modulation that might play key roles in chickpea heat tolerance. This study potentially contributes to improved stress resilience by advancing our understanding on the mechanisms of heat tolerance in chickpea

Interaction of Nitric Oxide with Phytohormones under Drought Stress

Plants are often exposed to a plethora of stress conditions such as salinity, extreme temperatures, drought, and heavy metals that can greatly impact farmer’s income. Nitric oxide (NO) has been implicated in resistance to various plant stresses and hence gaining increasing attention from plant researchers. NO mediate various abiotic and biotic stresses in plants including drought stress. However, it is still unclear about the actual involvement of NO in drought stress responses at a whole plant level. Whether NO act alone or in coherence with other phytohormones and signaling molecules is an open question till now. Here we summarized the interaction of NO with the well-known phytohormones in coping with the drought stress

Nitric Oxide as a Signal in Inducing Secondary Metabolites During Plant Stress

Secondary metabolites are the major defense elements of plants against biotic and abiotic stress conditions. They are diverse and valuable natural products induced by a variety of environmental and developmental cues. In recent years, NO has been successfully used as elicitor to stimulate secondary metabolite accumulation in plants. Emerging evidence has established the significant role of NO in plant growth and defense responses in plants. Several abiotic and biotic stress factors can induce NO-mediated regulation of the biosynthetic pathways of metabolites that can consequently alter their biological reaction toward the given stress. Moreover, exogenous treatments with NO donors also enhanced the accumulation of secondary metabolites including phenolics, flavonoids, and caffeic acid derivatives in several species suggesting the importance of NO accumulation for the secondary metabolic production. Complete elucidation of its role in the production of such secondary metabolites which are pharmaceutically significant is very essential for improving the large-scale commercial production and enhancing stress resilience in plants. Although several reports suggested the induction of secondary metabolites and NO against a range of stress factors, to establish link between NO and secondary metabolites under stress needs a deeper investigation. This compilation chiefly summarize NO biosynthesis, signaling, and functions under abiotic stress in plants highlighting what is currently known about secondary metabolite induction by NO in plants

Insights Into the Nitric Oxide Mediated Stress Tolerance in Plants

During the last two decades, several studies have established nitric oxide (NO) as a crucial signaling molecule during plant stress responses. NO protect plants from stressful conditions mostly through the activation of antioxidant defense, by maintaining metabolic homeostasis, by altering the gene transcription and posttranslational protein modifications. So far, most of the NO functions have been explored based on manipulation of endogenous NO levels by exogenous donors/scavengers or through mutants and transgenics. However, it is hard to draw any clear conclusions, since most of these studies are not uniform, being rather superficial without exploring the underlying signaling pathways. Indeed, the integration of the crosstalk events between NO and other signaling molecules under stress responses is also very critical. Importantly, lack of complete understanding of its production and signaling cascade is a serious setback for further elucidation by genetic and molecular approaches. Therefore, a step forward now will be to explore more NO responsive genes, proteins, and their networks under stress to serve as a key resource for further NO research

Complex and shifting interactions of phytochromes regulate fruit development in tomato

Tomato fruit ripening is a complex metabolic process regulated by a genetical hierarchy. A subset of this process is also modulated by light-signaling, as mutants encoding negative regulators of phytochrome signal transduction, show higher accumulation of carotenoids. In tomato phytochromes are encoded by a multi-gene family, namely PhyA, PhyB1, PhyB2, PhyE and PhyF, however, their contribution to fruit development and ripening has not been examined. Using single phytochrome mutants- phyA, phyB1 and phyB2 and multiple mutants- phyAB1, phyB1B2 and phyAB1B2, we compared the on-vine transitory phases of ripening till fruit abscission. The phyAB1B2 mutant showed accelerated transitions during ripening with shortest time to fruit abscission. Comparison of transition intervals in mutants indicated a phase-specific influence of different phytochrome species either singly or in combination on the ripening process. Examination of off-vine ripened fruits indicated that ripening specific carotenoid accumulation was not obligatorily dependent on light and even dark incubated fruits accumulated carotenoids. The accumulation of transcripts and carotenoids in off-vine and on-vine ripened mutant fruits indicated a complex and shifting phase-dependent modulation by phytochromes(s). Our results indicate that in addition to regulating carotenoid levels in tomato fruits, phytochrome(s) also regulate the time required for phase transitions during ripening

Tomato Fruit Ripening: Ethylene as a major player

Tomato (Solanum lycopersicum) is one of the important vegetable crops in India and it ranks next to potato in consumption. It has also emerged as the model plant for climacteric fruit ripening for a combination of scientific and agricultural reasons. The ripening of fleshy fruits is carried out by a series of biochemical, physiological and structural changes that make the fruit attractive and palatable to the consumer. During the process of fruit ripening, changes in texture, color, flavor and aroma occur in addition to alteration in levels of vitamins and antioxidants. In climacteric fruits like tomato, ethylene production is necessary for initiation and completion of the process of fruit ripening. Ethylene is a gaseous hormone that play a critical in regulating a number of physiological and developmental events in plants. Various facets of fruit ripening are stimulated by ethylene, though it certainly is not the only contributing component. A greater understanding of the role of ethylene in fruit ripening and interactions of other hormones and developmental factors in ripening can facilitate the identification of target loci to enhance fruit quality, yield and nutritional value

The leaf proteome signatures provide molecular insights into the abiotic stress tolerance in chickpea: A priming and proteomics approach

Understanding the proteomic differences under stress conditions is a promising approach for global food security by providing useful insights into the stress tolerance mechanisms in plants. In our study we focused on developing the leaf proteome signatures associated with major abiotic stresses in chickpea (Cicer arietinum L.) such as drought, heat, salt were compared to the control using comparative label-free quantitative proteomics. The proteomic analysis identified a total of 590, 248 & 797 differentially regulated proteins by drought, heat and salt stress respectively. Several crucial stress induced and repressed proteins were identified and categorized based on ontology and pathway analysis. The proteins which are essentially related to the electron transport chain in photosynthesis, aminoacid biosynthesis, ribosome synthesis and secondary metabolite synthesis may play key roles in inducing heat and drought tolerance in chickpea. On the other hand, priming with exogenous application of certain plant protecting compounds has become increasingly popular technique in plant stress biology. Despite its relevance as a plant growth and stress regulator, the current knowledge about the mechanism of nitric oxide (NO) action is still limited. Our study provided evidence that the foliar application of NO donor can enhance stress tolerance by modulating a number of proteins in chickpea. Proteomic studies on priming in the context of abiotic stress identified key protein targets and signaling pathways that are being involved in the stress alleviation. Understanding the active metabolic adjustments in tolerant genotype under stress and inducing the stress tolerance in sensitive genotype by exogenous NO application offers a comprehensive and systematic approach to tackle abiotic stress in chickpea. This study offer valuable insights on the mechanisms of stress tolerance that help plant biologists to develop designer crops to withstand a wider range of climatic variability under the current scenario of climate change