Physio-biochemical assessment and expression analysis of genes associated with drought tolerance in sugarcane (Saccharum spp. hybrids) exposed to GA3 at grand growth stage

Exogenous GA3 Enhances Nitrogen Uptake and Metabolism under Low Nitrate Conditions in 'Duli' (Pyrus betulifolia Bunge) Seedlings

'Duli' (Pyrus betulifolia Bunge) is one of the main rootstocks of pear trees in China. Gibberellin (GA) is a key plant hormone and the roles of GA in nitrate (NO3-) uptake and metabolism in plants remain unclear. In this study, we investigated the effects of exogenous GA3 on the N metabolism of 'Duli' seedlings under NO3- deficiency. The results showed that exogenous GA3 significantly improves 'Duli' growth under NO3- deficiency. On the one hand, GA3 altered the root architecture, increased the content of endogenous hormones (GA3, IAA, and ZR), and enhanced photosynthesis; on the other hand, it enhanced the activities of N-metabolizing enzymes and the accumulation of N, and increased the expression levels of N absorption (PbNRT2) and the metabolism genes (PbNR, PbGILE, PbGS, and PbGOGAT). However, GA3 did not delay the degradation of chlorophyll. Paclobutrazol had the opposite effect on growth. Overall, GA3 can increase NO3- uptake and metabolism and relieve the growth inhibition of 'Duli' seedlings under NO3- deficiency.

Assessment of physio-biochemical assessment and gene expression analysis of sugarcane genotypes under water stress

BACKGROUND

Sugarcane, an economically important crop cultivated for its unique character of accumulating sucrose into its stalk and the world's major crop according to production quantity. Sugarcane production is negatively influenced by abiotic stresses because it faces all types of environments due to its long-life cycle period. Among the various abiotic stresses, drought is one of the major limiting factors creates obstacle in sugarcane production. Thus, an attempt was made to assess the molecular insights into sugarcane genotypes under water stress. A preliminary screening was done in ten sugarcane genotypes grown under semi-arid region of India through physiological, biochemical and antioxidant responses of these genotypes under two water deficit levels.

METHODS

In the current study, drought was imposed on ten sugarcane genotypes during their formative stage (110 DAP) by depriving them of irrigation. A pot experiment was carried out to see how several commercial sugarcane genotypes responded to water scarcity. Sugarcane received two treatments, the first after 125 days and the second after 140 days. The physio-biochemical and antioxidant responses recorded were RWC, MSI, SCMR, Proline accumulation, SOD, Catalase, Peroxidase and Lipid peroxidation. The significant variations were recorded in responses of all genotypes. On the basis of physio-biochemical, three genotypes Cos 98,014, Cos 13,235 and Colk 14,201 were selected for differential gene expression pattern analysis. The total RNA was isolated and reverse transcribe to cDNA and real time PCR was performed for expression analysis under 10 genes.

RESULTS

Under drought conditions, all sugarcane genotypes showed significantly decreased RWC, chlorophyll content, and MSI. However, when water was scarce, proline buildup, malondialdehyde (MDA) contents, enzymatic antioxidant activity (CAT, POD, and SOD), and contents all increased dramatically. Finally, in all physiological and biochemical parameters, Co 98,014 genotype displayed superior adaptation responses to drought stress, followed by Co 018, Cos 13,235, and Colk 14,201. For gene expression analysis out of 21 genes, 10 genes were expressed in sugarcane genotypes, in which 7 genes (Shbbx2, Shbbx3, Shbbx4, Shbbx5, Shbbx8, Shbbx15 and Shbbx20) were upregulated and 3 genes (Shbbx1, Shbbx16 and Shbbx17) were downregulated.

CONCLUSION

The statistical analysis conducted in this study demonstrated that drought stress had a negative impact on physiological responses, including RWC, SPAD, and MSI, in sugarcane crops. However, it was found that the crops were able to survive in these stress conditions by increasing their biochemical parameters, all while maintaining their growth and function.

Transcriptomic and Proteomic Landscape of Sugarcane Response to Biotic and Abiotic Stressors

Sugarcane, a C₄ plant, provides most of the world's sugar, and a substantial amount of renewable bioenergy, due to its unique sugar-accumulating and feedstock properties. Brazil, India, China, and Thailand are the four largest sugarcane producers worldwide, and the crop has the potential to be grown in arid and semi-arid regions if its stress tolerance can be improved. Modern sugarcane cultivars which exhibit a greater extent of polyploidy and agronomically important traits, such as high sugar concentration, biomass production, and stress tolerance, are regulated by complex mechanisms. Molecular techniques have revolutionized our understanding of the interactions between genes, proteins, and metabolites, and have aided in the identification of the key regulators of diverse traits. This review discusses various molecular techniques for dissecting the mechanisms underlying the sugarcane response to biotic and abiotic stresses. The comprehensive characterization of sugarcane's response to various stresses will provide targets and resources for sugarcane crop improvement.

Targeted and untargeted metabolomics reveals deep analysis of drought stress responses in needles and roots of Pinus taeda seedlings

Drought stress is one of major environmental stresses affecting plant growth and yield. Although Pinus taeda trees are planted in rainy southern China, local drought sometime occurs and can last several months, further affecting their growth and resin production. In this study, P. taeda seedlings were treated with long-term drought (42 d), and then targeted and untargeted metabolomics analysis were carried out to evaluate drought tolerance of P. taeda. Targeted metabolomics analysis showed that levels of some sugars, phytohormones, and amino acids significantly increased in the roots and needles of water-stressed (WS) P. taeda seedlings, compared with well-watered (WW) pine seedlings. These metabolites included sucrose in pine roots, the phytohormones abscisic acid and sacylic acid in pine needles, the phytohormone gibberellin (GA4) and the two amino acids, glycine and asparagine, in WS pine roots. Compared with WW pine seedlings, the neurotransmitter acetylcholine significantly increased in needles of WS pine seedlings, but significantly reduced in their roots. The neurotransmitters L-glutamine and hydroxytyramine significantly increased in roots and needles of WS pine seedlings, respectively, compared with WW pine seedlings, but the neurotransmitter noradrenaline significantly reduced in needles of WS pine seedlings. Levels of some unsaturated fatty acids significantly reduced in roots or needles of WS pine seedlings, compared with WW pine seedlings, such as linoleic acid, oleic acid, myristelaidic acid, myristoleic acid in WS pine roots, and palmitelaidic acid, erucic acid, and alpha-linolenic acid in WS pine needles. However, three saturated fatty acids significantly increased in WS pine seedlings, i.e., dodecanoic acid in WS pine needles, tricosanoic acid and heptadecanoic acid in WS pine roots. Untargeted metabolomics analysis showed that levels of some metabolites increased in WS pine seedlings, especially sugars, long-chain lipids, flavonoids, and terpenoids. A few of specific metabolites increased greatly, such as androsin, piceatanol, and panaxatriol in roots and needles of WS pine seedlings. Comparing with WW pine seedlings, it was found that the most enriched pathways in WS pine needles included flavone and flavonol biosynthesis, ABC transporters, diterpenoid biosynthesis, plant hormone signal transduction, and flavonoid biosynthesis; in WS pine roots, the most enriched pathways included tryptophan metabolism, caffeine metabolism, sesquiterpenoid and triterpenoid biosynthesis, plant hormone signal transduction, biosynthesis of phenylalanine, tyrosine, and tryptophan. Under long-term drought stress, P. taeda seedlings showed their own metabolomics characteristics, and some new metabolites and biosynthesis pathways were found, providing a guideline for breeding drought-tolerant cultivars of P. taeda.

Impact of Agroclimatic Variables on Proteogenomics in Sugar Cane (Saccharum spp.) Plant Productivity

Sugar cane (Saccharum spp. hybrids) is a major crop for sugar and renewable bioenergy worldwide, grown in arid and semiarid regions. China, the world's fourth-largest sugar producer after Brazil, India, and the European Union, all share ∼80% of the global production, and the remaining ∼20% of sugar comes from sugar beets, mostly grown in the temperate regions of the Northern Hemisphere, also used as a raw material in production of bioethanol for renewable energy. In view of carboxylation strategies, sugar cane qualifies as one of the best C4 crop. It has dual CO2 concentrating mechanisms located in its unique Krantz anatomy, having dimorphic chloroplasts located in mesophylls and bundle sheath cells for integrated operation of C4 and C3 carbon fixation cycles, regulated by enzymes to upgrade/sustain an ability for improved carbon assimilation to acquire an optimum carbon economy by producing enhanced plant biomass along with sugar yield under elevated temperature and strong irradiance with improved water-use efficiency. These superior intrinsic physiological carbon metabolisms encouraged us to reveal and recollect the facts for moving ahead with the molecular approaches to reveal the expression of proteogenomics linked with plant productivity under abiotic stress during its cultivation in specific agrizones globally.

A Circular Economy Approach to Restoring Soil Substrate Ameliorated by Sewage Sludge with Amendments

This study examined the use of an artificial soil substrate in a mine waste reclamation area and its effect on plant metabolic functions. Research was conducted by determining the relationship between the plants’ biochemical features and the properties of plant growth medium derived from post-flotation coal waste, sewage sludge, crushed stone and fly ash on the surface of the mine waste disposal area. Trees and shrubs were established on the material and allowed to grow for eight years. The study determined that the applied plants and the naturally occurring Taraxacum officinale were suitable for physio-biochemical assessment, identification of derelict areas and reclamation purposes. An evaluation of a soil substrate applied to post-mining areas indicated that it was beneficial for plant growth since it activated the metabolic functions of herbaceous plants, shrubs, and trees. The study showed that soil substrate can be targeted to improve plant stress tolerance to potentially toxic elements (PTEs). These data suggest the potential for growth and slower susceptible response to Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn. It is possible that the constructed soil-substitute substrate (biosolid material) would be an effective reclamation treatment in areas where natural soil materials are polluted by PTEs. This observation may reflect a more efficient use of soil substrate released from the cycling of organic biogene pools, in accordance with the circular economy approach. In further studies related to land reclamation using sewage sludge amendments, it would be necessary to extend the research to other stress factors, such as salinity or water deficiency.

Foliar application of silicon boosts growth, photosynthetic leaf gas exchange, antioxidative response and resistance to limited water irrigation in sugarcane (Saccharum officinarum L.)

Plant cell and water relationship regulates morphological, physiological and biochemical characteristics to optimize carboxylation for enhanced biomass yield in sugarcane. Insufficient water irrigation is one of the serious problems to impair potential yield of agriculturally important sugarcane cash crop by loss in plant performance. Our study aims to reveal consequences of foliar spray of silicon (Si) using calcium metasilicate powder (Wollastonite, CaO.SiO₂) to alleviate the adverse effects of limited water irrigation in sugarcane. Silicon (0, 50, 100 and 500 ppm) was applied as foliar spray on normally grown 45 days old sugarcane plants. Further, these plants were raised at half field capacity (50%) using water irrigation precisely up to 90 days under open environmental variables. Consequently, restricted irrigation impaired plant growth-development, leaf relative water content (%), photosynthetic pigments, SPAD unit, photosynthetic performance, chlorophyll fluorescence variable yield (Fv/Fm) and biomass yield. Notably, it has enhanced values of proline, hydrogen peroxide (H₂O₂), malondialdehyde (MDA), antioxidative defense enzyme molecules viz., catalase (CAT), ascorbate peroxidase (APx) and superoxide dismutase (SOD). The foliar spray of Si defended sugarcane plants from limited water irrigation stress as Si quenched harmful effect of water-deficit and also enhanced the operation of antioxidant defense machinery for improved sugarcane plant performance suitably favored stomatal dynamics for photosynthesis and plant productivity.

Investigation of Defensive Role of Silicon during Drought Stress Induced by Irrigation Capacity in Sugarcane: Physiological and Biochemical Characteristics

Water stress may become one of the most inevitable factors in years to come regulating crop growth, development, and productivity globally. The application of eco-friendly stress mitigator may sustain physiological fitness of the plants as uptake and accumulation of silicon (Si) found to alleviate stress with plant performance. Our study focused on the mitigative effects of Si using calcium metasilicate (wollastonite powder, CaO·SiO₂) in sugarcane (Saccharum officinarum L.) prior to the exposure of water stress created by the retention of 50-45% soil moisture capacity. Si (0, 50, 100, and 500 ppm L^-1) was supplied through soil irrigation in S. officinarum L. grown at about half of the soil moisture capacity for a period of 90 days. Water stress impaired plant growth, biomass, leaf relative water content, SPAD value, photosynthetic pigments capacity, and photochemical efficiency (F _v/F _m) of photosystem II. The levels of antioxidative defense-induced enzymes, viz., catalase, ascorbate peroxidase, and superoxide dismutase, enhanced. Silicon-treated plants expressed positive correlation with their performance index. A quadratic nonlinear relation observed between loss and gain (%) in physiological and biochemical parameters during water stress upon Si application. Si was found to be effective in restoring the water stress injuries integrated to facilitate the operation of antioxidant defense machinery in S. officinarum L. with improved plant performance index and photosynthetic carbon assimilation.

Crosstalk between phytohormones and secondary metabolites in the drought stress tolerance of crop plants: A review

Drought stress negatively affects crop performance and weakens global food security. It triggers the activation of downstream pathways, mainly through phytohormones homeostasis and their signaling networks, which further initiate the biosynthesis of secondary metabolites (SMs). Roots sense drought stress, the signal travels to the above-ground tissues to induce systemic phytohormones signaling. The systemic signals further trigger the biosynthesis of SMs and stomatal closure to prevent water loss. SMs primarily scavenge reactive oxygen species (ROS) to protect plants from lipid peroxidation and also perform additional defense-related functions. Moreover, drought-induced volatile SMs can alert the plant tissues to perform drought stress mitigating functions in plants. Other phytohormone-induced stress responses include cell wall and cuticle thickening, root and leaf morphology alteration, and anatomical changes of roots, stems, and leaves, which in turn minimize the oxidative stress, water loss, and other adverse effects of drought. Exogenous applications of phytohormones and genetic engineering of phytohormones signaling and biosynthesis pathways mitigate the drought stress effects. Direct modulation of the SMs biosynthetic pathway genes or indirect via phytohormones' regulation provides drought tolerance. Thus, phytohormones and SMs play key roles in plant development under the drought stress environment in crop plants.

Predication of Photosynthetic Leaf Gas Exchange of Sugarcane (Saccharum spp) Leaves in Response to Leaf Positions to Foliar Spray of Potassium Salt of Active Phosphorus under Limited Water Irrigation

Sufficient water and fertilizer inputs in agriculture play a major role in crop growth, production, and quality. In this study, the response of sugarcane to limited water irrigation and foliar application of potassium salt of active phosphorus (PSAP) for photosynthetic responses were examined, and PSAP's role in limited water irrigation management was assessed. Sugarcane plants were subjected to limited irrigation (95-90 and 45-40% FC) after three months of germination, followed by a foliar spray (0, 2, 4, 6, and 10 M) of PSAP. The obtained results indicated that limited water irrigation negatively affected sugarcane growth and reduced leaf gas exchange activities. However, the application of PSAP increased the photosynthetic activities by protecting the photosynthetic machinery during unfavorable conditions. Mathematical modeling, a Skewed model, was developed and compared with the existing Gaussian model to describe the photosynthetic responses of sugarcane leaves under the limited irrigation with and without PSAP application. The models fitted well with the observed values, and the predicted photosynthetic parameters were in close relationship with the obtained results. The Skewed model was found to be better than the Gaussian model in describing the photosynthetic parameters of plant leaves positioned over a stem of limited water irrigation and applied PSAP application and is recommended for further application.