Plant-Derived Smoke Affects Biochemical Mechanism on Plant Growth and Seed Germination.

The role of plant-derived smoke, which is changed in mineral-nutrient status, in enhancing germination and post-germination was effectively established. The majority of plant species positively respond to plant-derived smoke in the enhancement of seed germination and plant growth. The stimulatory effect of plant-derived smoke on normally growing and stressed plants may help to reduce economic and human resources, which validates its candidature as a biostimulant. Plant-derived smoke potentially facilitates the early harvest and increases crop productivity. Karrikins and cyanohydrin are the active compound in plant-derived smoke. In this review, data from the latest research explaining the effect of plant-derived smoke on morphological, physiological, biochemical, and molecular responses of plants are presented. The pathway for reception and interaction of compounds of plant-derived smoke at the cellular and molecular level of plant is described and discussed.

Molecular Responses of Maize Shoot to a Plant Derived Smoke Solution.

Plant-derived smoke has effects on plant growth. To find the molecular mechanism of plant-derived smoke on maize, a gel-free/label-free proteomic technique was used. The length of root and shoot were increased in maize by plant-derived smoke. Proteomic analysis revealed that 2000 ppm plant-derived smoke changed the abundance of 69 proteins in 4-days old maize shoot. Proteins in cytoplasm, chloroplast, and cell membrane were altered by plant-derived smoke. Catalytic, signaling, and nucleotide binding proteins were changed. Proteins related to sucrose synthase, nucleotides, signaling, and glutathione were significantly increased; however, cell wall, lipids, photosynthetic, and amino acid degradations related proteins were decreased. Based on proteomic and immunoblot analyses, ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) was decreased; however, RuBisCO activase was not changed by plant-derived smoke in maize shoot. Ascorbate peroxidase was not affected; however, peroxiredoxin was decreased by plant-derived smoke. Furthermore, the results from enzyme-activity and mRNA-expression analyses confirmed regulation of ascorbate peroxidase and the peroxiredoxinin reactive oxygen scavenging system. These results suggest that increases in sucrose synthase, nucleotides, signaling, and glutathione related proteins combined with regulation of reactive oxygen species and their scavenging system in response to plant-derived smoke may improve maize growth.

Soybean proteomics for unraveling abiotic stress response mechanism.

Plant response to abiotic stresses depends upon the fast activation of molecular cascades involving stress perception, signal transduction, changes in gene and protein expression and post-translational modification of stress-induced proteins. Legumes are extremely sensitive to flooding, drought, salinity and heavy metal stresses, and soybean is not an exception of that. Invention of immobilized pH gradient strips followed by advancement in mass spectrometry has made proteomics a fast, sensitive and reliable technique for separation, identification and characterization of stress-induced proteins. As the functional translated portion of the genome plays an essential role in plant stress response, proteomic studies provide us a finer picture of protein networks and metabolic pathways primarily involved in stress tolerance mechanism. Identifying master regulator proteins that play key roles in the abiotic stress response pathway is fundamental in providing opportunities for developing genetically engineered stress-tolerant crop plants. This review highlights recent contributions in the field of soybean biology to comprehend the complex mechanism of abiotic stress acclimation. Furthermore, strengths and weaknesses of different proteomic methodologies of extracting complete proteome and challenges and future prospects of soybean proteome study both at organ and whole plant levels are discussed in detail to get new insights into the plant abiotic stress response mechanism.

Plant-Derived Smoke Mitigates the Inhibitory Effects of the Auxin Inhibitor 2,3,5-Triiodo Benzoic Acid (TIBA) by Enhancing Root Architecture and Biochemical Parameters in Maize.

The present study was designed to investigate and compare the effects of plant-derived smoke (PDS) and auxin (IAA and IBA) on maize growth under the application of 2,3,5-triiodo benzoic acid (TIBA). For this purpose, indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA), each at a concentration of 10 ppm, along with PDS at a ratio of 1:500 (v/v) were used alone and in combination with 10 ppm of TIBA. The results indicate that the germination percentage (%) of maize seeds was enhanced under IAA, IBA and PDS treatment. However, IAA and IBA resulted in reduced germination when applied in combination with TIBA. Importantly, the germination percentage (%) was improved by PDS under TIBA treatment. The analysis of seedling height, length of leaves, and number of primary, seminal and secondary/lateral roots showed improvement under individual treatments of IAA and IBA, PDS and PDS + TIBA treatment, while these values were reduced under IAA + TIBA and IBA + TIBA application. Chlorophyll content, total soluble sugars and antioxidative enzymatic activity including POD and SOD increased in seedlings treated with PDS alone or both PDS and TIBA, while in seedlings treated with IAA and TIBA or IBA and TIBA, their levels were decreased. APX and CAT responded in the opposite way-under IAA, IBA and PDS treatment, their levels were found to be lower than the control (simple water treatment), while TIBA treatment with either IAA, IBA or PDS enhanced their levels as compared to the control. These results reveal that PDS has the potential to alleviate the inhibitory effects of TIBA. This study highlights the role of PDS in preventing TIBA from blocking the auxin entry sites.

A comparative proteomics analysis in roots of soybean to compatible symbiotic bacteria under flooding stress.

A proteomics approach was used to evaluate the effects of flooding stress on early symbiotic interaction between soybean roots and soil bacteria, Bradyrhizobium japonicum. Three-day-old soybean was inoculated with B. japonicum followed by flooding. The number of root hairs in seedlings, without or with flooding stress, was increased after 3 days of inoculation. Proteins were extracted from roots and separated by two-dimensional polyacrylamide gel electrophoresis. Out of 219 protein spots, 14 and 8 proteins were increased and decreased, respectively, by inoculation under flooding compared with without flooding. These proteins were compared in untreated and flooded seedlings. Increased level of 6 proteins in flooded seedlings compared with untreated seedlings was suppressed by inoculation in seedlings under flooding. They were related to disease/defense, protein synthesis, energy, and metabolism. Differential abundance of glucan endo-1,3-beta-glucosidase, phosphoglycerate kinase, and triosephosphate isomerase, based on their localization in middle and tip of root, indicated that they might be related to increase in number of root hairs. These results suggest that disease/defense, energy, and metabolism-related proteins may be particularly subjected to regulation in flooded soybean seedlings, when inoculated with B. japonicum and that this regulation may lead to increase in number of root hair during early symbiotic differentiation.

Analysis of response mechanism in soybean under low oxygen and flooding stresses using gel-base proteomics technique.

A proteomics approach was used to analyze the response mechanism in soybean seedlings under low oxygen and flooding stresses. Three-day-old soybean seedlings were subjected to low oxygen and flooding stresses. Growth of root was suppressed in both stresses with more extent of suppression in flooded seedlings at 3 and 6 days following the treatments. Proteins were extracted from roots and separated by two-dimensional polyacrylamide gel electrophoresis. Of total 1,233 protein spots, 27 protein spots were commonly changed under low oxygen and flooding stresses; while the differential change in 4 and 18 protein spots was specific to low oxygen and flooding stresses, respectively. Proteins related to metabolism and energy were increased; while protein destination/storage related proteins were decreased commonly under low oxygen and flooding stresses. Protein specie, TCP domain class transcription factor was decreased specifically under low oxygen stress; while decrease of nine proteins related to metabolism, protein destination/storage and disease/defense was specific in flooded seedlings. The decrease in majority of the proteins related to protein destination/storage specifically in flooded seedlings implies the misfolding of proteins resulting in flooded injuries in an independent way of oxygen deprivation. These results suggest that decrease in proteins related to protein destination/storage and disease/defense causes more growth suppression in soybean seedlings under flooding stress compared to low oxygen stress.

Synergistic Effects of Zinc Oxide Nanoparticles and Bacteria Reduce Heavy Metals Toxicity in Rice (Oryza sativa L.) Plant.

Heavy metals (HMs) are toxic elements which contaminate the water bodies in developing countries because of their excessive discharge from industrial zones. Rice (Oryza sativa L) crops are submerged for a longer period of time in water, so irrigation with HMs polluted water possesses toxic effects on plant growth. This study was initiated to observe the synergistic effect of bacteria (Bacillus cereus and Lysinibacillus macroides) and zinc oxide nanoparticles (ZnO NPs) (5, 10, 15, 20 and 25 mg/L) on the rice that were grown in HMs contaminated water. Current findings have revealed that bacteria, along with ZnO NPs at lower concentration, showed maximum removal of HMs from polluted water at pH 8 (90 min) as compared with higher concentrations. Seeds primed with bacteria grown in HM polluted water containing ZnO NPs (5 mg/L) showed reduced uptake of HMs in root, shoot and leaf, thus resulting in increased plant growth. Furthermore, their combined effects also reduced the bioaccumulation index and metallothionine (MTs) content and enhanced the tolerance index of plants. This study suggested that synergistic treatment of bacteria with lower concentrations of ZnO NPs helped plants to reduce heavy metal toxicity, especially Pb and Cu, and enhanced plant growth.

Proteomic analysis of the promotive effect of plant-derived smoke on plant growth of chickpea.

Plant-derived smoke plays a key role in seed germination and plant growth. To investigate the effect of plant-derived smoke on chickpea, a gel-free/label-free proteomic technique was used. Germination percentage, root/shoot length, and fresh biomass were increased in chickpea treated with 2000 ppm plant-derived smoke within 6 days. On treatment with 2000 ppm plant-derived smoke for 6 days, the abundance of 90 proteins including glycolysis-related proteins significantly changed in chickpea root. Proteins related to signaling and transport were increased; however, protein metabolism, cell, and cell wall were decreased. The sucrose synthase for starch degradation was increased and total soluble sugar was induced. The proteins for nitrate pathway were increased and nitrate content was improved. On the other hand, although secondary metabolism related proteins were decreased, flavonoid contents were increased. Based on proteomic and immuno-blot analyses, proteins related to redox homeostasis were decreased and increased in root and shoot, respectively. Furthermore, fructose­bisphosphate aldolase was increased; while, phosphotransferase and phosphoglycero mutase were decreased in glycolysis. In addition, phosphoglyceraldehyde­3­phosphate dehydrogenase and glutamine synthetase related genes were up-regulated. These results suggest that plant-derived smoke improves early stage of growth in chickpea with the balance of many cascades such as glycolysis, redox homeostasis, and secondary metabolism. BIOLOGICAL SIGNIFICANCE: The current study examined the effects of plant-derived smoke on root of chickpea seedlings using a gel-free/label-free proteomic technique. Based on functional categorization of results from proteomics, proteins related to glycolysis, signaling, transport, protein metabolism, cell wall, and cell were predominantly changed in chickpea. The proteins related to carbohydrate and nitrate pathways were increased, while, those of secondary metabolism were decreased. Physiological analysis indicated that flavonoid, total soluble sugar, and nitrate content were increased in root of chickpea treated with plant-derived smoke for 6 days. Moreover, accumulated protein abundance of glyceraldehyde­3­phosphate dehydrogenase and fructose-bisphosphate aldolase was in agreement with immuno-blot results, which suggests that glycolysis process might be enhanced in root of chickpea in response to plant-derived smoke.

Analysis of proteomic changes in roots of soybean seedlings during recovery after flooding.

A proteomic approach was used to identify proteins involved in post-flooding recovery in soybean roots. Two-day-old soybean seedlings were flooded with water for up to 3 days. After the flooding treatment, seedlings were grown until 7 days after sowing and root proteins were then extracted and separated using two-dimensional polyacrylamide gel electrophoresis (2-DE). Comparative analysis of 2-D gels of control and 3 day flooding-experienced soybean root samples revealed 70 differentially expressed protein spots, from which 80 proteins were identified. Many of the differentially expressed proteins are involved in protein destination/storage and metabolic processes. Clustering analysis based on the expression profiles of the 70 differentially expressed protein spots revealed that 3 days of flooding causes significant changes in protein expression, even during post-flooding recovery. Three days of flooding resulted in downregulation of ion transport-related proteins and upregulation of proteins involved in cytoskeletal reorganization, cell expansion, and programmed cell death. Furthermore, 7 proteins involved in cell wall modification and S-adenosylmethionine synthesis were identified in roots from seedlings recovering from 1 day of flooding. These results suggest that alteration of cell structure through changes in cell wall metabolism and cytoskeletal organization may be involved in post-flooding recovery processes in soybean seedlings.

Organ-specific proteomics analysis for identification of response mechanism in soybean seedlings under flooding stress.

Flooding is one of the severe environmental factors which impair growth and yield in soybean plant. To investigate the organ specific response mechanism of soybean under flooding stress, changes in protein species were analyzed using a proteomics approach. Two-day-old soybeans were subjected to flooding for 5 days. Proteins were extracted from root, hypocotyl and leaf, and separated by two-dimensional polyacrylamide gel electrophoresis. In root, hypocotyl and leaf, 51, 66 and 51 protein species were significantly changed, respectively, under flooding stress. In root, metabolism related proteins were increased; however these proteins were decreased in hypocotyl and leaf. In all 3 organs, cytoplasm localized proteins were decreased, and leaf chloroplastic proteins were also decreased. Isoflavone reductase was commonly decreased at protein level in all 3 organs; however, mRNA of isoflavone reductase gene was up-regulated in leaf under flooding stress. Biophoton emission was increased in all 3 organs under flooding stress. The up-regulation of isoflavone reductase gene at transcript level; while decreased abundance at protein level indicated that flooding stress affected the mRNA translation to proteins. These results suggest that concurrence in expression of isoflavone reductase gene at mRNA and protein level along with imbalance in other disease/defense and metabolism related proteins might lead to impaired growth of root, hypocotyl and leaf of soybean seedlings under flooding stress.