New insights into the evolution of SPX gene family from algae to legumes; a focus on soybean.

BACKGROUND: SPX-containing proteins have been known as key players in phosphate signaling and homeostasis. In Arabidopsis and rice, functions of some SPXs have been characterized, but little is known about their function in other plants, especially in the legumes. RESULTS: We analyzed SPX gene family evolution in legumes and in a number of key species from algae to angiosperms. We found that SPX harboring proteins showed fluctuations in domain fusions from algae to the angiosperms with, finally, four classes appearing and being retained in the land plants. Despite these fluctuations, Lysine Surface Cluster (KSC), and the third residue of Phosphate Binding Sites (PBS) showed complete conservation in almost all of SPXs except few proteins in Selaginella moellendorffii and Papaver sumniferum, suggesting they might have different ligand preferences. In addition, we found that the WGD/segmentally or dispersed duplication types were the most frequent contributors to the SPX expansion, and that there is a positive correlation between the amount of WGD contribution to the SPX expansion in individual species and its number of EXS genes. We could also reveal that except SPX class genes, other classes lost the collinearity relationships among Arabidopsis and legume genomes. The sub- or neo-functionalization of the duplicated genes in the legumes makes it difficult to find the functional orthologous genes. Therefore, we used two different methods to identify functional orthologs in soybean and Medicago. High variance in the dynamic and spatial expression pattern of GmSPXs proved the new or sub-functionalization in the paralogs. CONCLUSION: This comprehensive analysis revealed how SPX gene family evolved from algae to legumes and also discovered several new domains fused to SPX domain in algae. In addition, we hypothesized that there different phosphate sensing mechanisms might occur in S. moellendorffii and P. sumniferum. Finally, we predicted putative functional orthologs of AtSPXs in the legumes, especially, orthologs of AtPHO1, involved in long-distance Pi transportation. These findings help to understand evolution of phosphate signaling and might underpin development of new legume varieties with improved phosphate use efficiency.

Postharvest treatments with γ-aminobutyric acid, methyl jasmonate, or methyl salicylate enhance chilling tolerance of blood orange fruit at prolonged cold storage.

BACKGROUND: Blood orange is sensitive to chilling injury (CI) depending on cultivar and storage temperature. Postharvest treatments with γ-aminobutyric acid (GABA), methyl jasmonate (MeJA), or methyl salicylate (MeSA) are known to alleviate CI. γ-Aminobutyric acid aqueous solution, applied at 20 and 40 mM, was vacuum-infiltrated at 30 kPa for 8 min at 20 °C. Methyl jasmonate or MeSA vapor treatments were applied separately at 50 and 100 µM by putting the fruit in 20 L plastic containers for 18 h at 20 °C. There have been no reports about postharvest treatments of GABA, MeJA, or MeSA on enhancing the tolerance of 'Moro' blood orange to chilling during long-term cold storage at 3 °C for 150 days, which was the subject of this study. RESULTS: All treatments significantly alleviated CI symptoms of blood orange manifested by lower electrolyte leakage (EL), malondialdehyde (MDA), hydrogen peroxide (H2 O2 ) concentrations, and higher proline content in flavedo during storage. The largest effects were obtained with 100, 50 µM, and 40 mM for MeSA, MeJA, and GABA, respectively, which enhanced the activity of the antioxidant enzymes catalase (CAT), ascorbate peroxidase (APX) and superoxide dismutase (SOD), and phenylalanine ammonia-lyase (PAL). On the other hand, these treatments suppressed peroxidase (POD) and polyphenol oxidase (PPO) activities. CONCLUSION: The mechanisms involved in enhancing the tolerance of 'Moro' blood orange to chilling could involve scavenging H2 O2 by increasing the activity of antioxidant enzymes, higher PAL/PPO activity ratio, and osmoregulation by increasing proline content. These changes led to the maintenance of the epidermis structure. This was confirmed by scanning electron microscopy (SEM) micrographs. © 2019 Society of Chemical Industry.

The potential of postharvest zinc treatment for preservation of pomegranate aril quality.

A short shelf life usually limits the distribution and supply of pomegranate arils. Since zinc (Zn) has an indispensable role in the nutrient integrity of our diet and is effective in suppressing pathogens, this study was done as two separate experiments of pre-harvest spraying and postharvest dipping of arils with two zinc supplements, including nano zinc oxide (nZnO) and zinc sulfate (ZnSO4). The optimized concentration of both sources was used in the experiment. The pre-harvest treatment failed to extend the shelf life of arils, and, ultimately, the arils decayed after 15 days. However, the postharvest zinc treatment significantly (P < 0.01) affected all measured indices. Also, zinc sulfate was more effective than nZnO. Zn uptake was higher in postharvest treatments because exogenous Zn was in direct contact with the aril surface. After dissolving in water, Zn ions in sulfate bind to the membrane of microorganisms and thus delay cell division and microbial growth cycle. The solubility of zinc oxide nanoparticles in water is poor. Using the ZnSO4 treatment (0.8%W/V) effectively maintained the values of titratable acidity (TA), total phenolic content (TPC), total soluble solids (TSS), anthocyanin content, and antioxidant activity. Also, this treatment significantly controlled weight loss in the arils.

Improving postharvest quality and vase life of cut rose flowers by pre-harvest foliar co-applications of γ-aminobutyric acid and calcium chloride.

Rose flowers (Rosa hybrida L.) are highly perishable and have a limited vase life. This study evaluated the effects of preharvest foliar applications of γ-aminobutyric acid (GABA) and calcium chloride (CaCl2), individually and combined, on antioxidant responses and vase life of cut Jumilia rose flowers. Treatments included foliar sprays of GABA at 0, 20, 40, and 60 mM and CaCl2 at 0, 0.75%, and 1.5%, applied in a factorial design within a completely randomized setup before harvest. Results showed GABA and CaCl2 interaction (especially, 60 mM GABA and 1.5% CaCl2) significantly increased enzymatic antioxidants including superoxide dismutase, catalase, and peroxidase, as well as non-enzymatic antioxidants such as flavonoids, carotenoids, phenolics, and antioxidant activity in petals compared to control. SOD activity in roses, treated with CaCl2 (1.5%) and GABA (60 mM), peaked at 7.86 units. mg-1 protein min-1, showing a nearly 2.93-fold increase over the control (2.68 units. mg-1 protein min-1). A parallel trend was observed for CAT activity. These treatments also reduced petal malondialdehyde content and polyphenol oxidase activity. Protein content and vase life duration increased in all treatments. Plants treated with a combination of GABA (20 mM) and CaCl2 (0.75%), GABA (60 mM) and CaCl2 (1.5%), or GABA (40 mM) individually exhibited the longest vase life duration. The co-application of GABA and CaCl2 improved the antioxidant activity and postharvest quality of cut roses by reducing PPO activity and MDA contents, increasing protein content and prolonging vase life. This treatment is a potential postharvest strategy to improve antioxidant capacity and delay senescence in cut roses.

Application of candidate endophytic fungi isolated from extreme desert adapted trees to mitigate the adverse effects of drought stress on maize (Zea mays L.).

The survival of plants under adverse conditions in desert habitats is related to microbial interactions, which can be an innovative strategy for reducing the effects of drought stress in colonized plants. In this study, two endophytic fungi, Trichoderma harzianum, and Fusarium solani, were recovered from the roots of trees in desert regions of Iran. A greenhouse experiment with two fungal agents (control, T. harzianum, F. solani, and T. harzianum + F. solani) and drought (100, 75, and 50% water-holding capacity) was performed on maize (Zea mays L.). Findings indicate that increasing drought levels negatively affect maize plant growth and physiological traits. However, the symbiotic relationship between fungal endophytes and maize roots increased fresh and dry biomass, root/shoot ratio, leaf area, relative water content, and membrane stability index compared with their control counterparts. Maize plants inoculated with endophytic fungi had 52.07, 40, 33.03, and 55.62% higher total phenolic, proline and soluble sugar concentrations, respectively than uninoculated controls. Photosynthetic parameters, including chlorophyll and carotenoid pigments, chlorophyll fluorescence, and gas exchange, were improved in the endophyte-treated plants. However, with increasing drought stress, maize plants colonized with endophytes, electrolyte leakage, and sub-stomatal CO2 concentrations decreased by 28.93% and 47.62%, respectively, compared to endophyte-free plants. When plants were exposed to higher levels of drought stress, endophytes were more effective in improving most parameters, and inoculation of maize seedlings with a combination of endophytes isolated from plants in harsh regions was more effective in increasing their tolerance to drought stress than individual inoculation of each fungus.

Integration of transcriptomic and metabolomic analyses provides insights into response mechanisms to nitrogen and phosphorus deficiencies in soybean.

Nitrogen (N) and phosphorus (P) are two essential plant macronutrients that can limit plant growth by different mechanisms. We aimed to shed light on how soybean respond to low nitrogen (LN), low phosphorus (LP) and their combined deficiency (LNP). Generally, these conditions triggered changes in gene expression of the same processes, including cell wall organization, defense response, response to oxidative stress, and photosynthesis, however, response was different in each condition. A typical primary response to LN and LP was detected also in soybean, i.e., the enhanced uptake of N and P, respectively, by upregulation of genes for the corresponding transporters. The regulation of genes involved in cell wall organization showed that in LP roots tended to produce more casparian strip, in LN more secondary wall biosynthesis occurred, and in LNP reduction in expression of genes involved in secondary wall production accompanied by cell wall loosening was observed. Flavonoid biosynthesis also showed distinct pattern of regulation in different conditions: more anthocyanin production in LP, and more isoflavonoid production in LN and LNP, which we confirmed also on the metabolite level. Interestingly, in soybean the nutrient deficiencies reduced defense response by lowering expression of genes involved in defense response, suggesting a role of N and P nutrition in plant disease resistance. In conclusion, we provide detailed information on how LN, LP, and LNP affect different processes in soybean roots on the molecular and physiological levels.

Essential Oil Variability of Superior Myrtle (Myrtus communis L.) Accessions Grown under the Same Conditions.

Myrtle (Myrtus communis L., Myrtaceae) has numerous applications in pharmacology, food technology, and cosmetic industry. The current research aimed at measuring variations in the leaf essential oil (EO) compositions of 14 superior myrtle accessions originating in natural habitats of south Iran. The plants were grown under greenhouse conditions. Fresh leaf samples were harvested in June 2021. Based on dry matter, the extractable amount of EO in the accessions ranged from 0.42% (BN2) to 2.6% (BN5). According to GC/MS analysis, the major compounds in the EO were α-pinene (2.35-53.09%), linalyl acetate (0-45.3%), caryophyllene oxide (0.97-21.8%), germacrene D (0-19.19%), α-humulene (0-18.97%), 1,8-cineole (0-18.0%), limonene (0-17.4%), and p-cymene (0-13.2%). These myrtle accessions were classified into four groups, including I: caryophyllene oxide/germacrene D/α-humulene/methyl eugenol chemotype; II: α-pinene/p-cymene/α-humulene and (E)-ß-caryophyllene; III: α-pinene/1,8-cineole, and linalool; IV: linalyl acetate/γ-terpinene/1,8, cineole/limonene. These classifications were established by considering the main EO components using hierarchical cluster analysis (HCA) and principal component analysis (PCA). In summary, this study provided new insights into available opportunities of selecting suitable genotypes for commercial cultivation purposes and planning breeding programs in the future.

Potential Role of Foliar Application of Azotobacter on Growth, Nutritional Value and Quality of Lettuce under Different Nitrogen Levels.

Vegetables can be treated with biofertilizers as an alternative to chemical fertilizers because of their low toxicity. We investigated the effects of foliar spraying of Azotobacter under different levels of nitrogen (100, 150 and 200 mg/L in nutrient solution) on the growth, nutritional value, nitrate accumulation and antioxidant enzyme activities of hydroponically grown lettuce. The experiment was laid out in a completely randomized design with four replicates in a factorial combination. Plants treated with Azotobacter and 200 mg/L nitrogen had greater leaf area and photosynthetic pigments than plants treated with 200 mg/L nitrogen without spraying with Azotobacter. Increasing nitrogen levels increased leaf number, fresh and dry weights, leaf area and nitrate accumulation in lettuce plants. Peroxidase (POD) activity increased by 95.4% at a nitrogen level of 200 mg/L compared to a nitrogen level of 100 mg/L. Ascorbate peroxidase (APX) activity and leaf phosphorous (P) and potassium (K) concentrations were the highest in plants treated with a nitrogen source of 100 mg/L without foliar application of Azotobacter. As nitrogen levels increased in all treatments, nitrate reductase (NR) activity decreased and reached a minimum at the 200 mg/L nitrogen level. In general, foliar application of Azotobacter sp. can be used to promote plant growth and reduce nitrate accumulation in lettuce.

Genetic diversity and inter-relationships of fruit bio-chemicals and antioxidant activity in Iranian wild blackberry species.

Blackberries are a rich source of bio-chemicals such as anthocyanins and polyphenolic antioxidants. The evaluation of the extent of variation among wild genetic resources can provide useful information for the establishment of effective conservation strategies and future breeding programs. In this study, variations and inter-relationship of berry weight, total phenol (TP), total soluble solids (TSS), titratable acidity (TA), ascorbic acid (AA), anthocyanin and antioxidant activity were estimated in their values among 57 accessions belonging to 4 different Rubus spp. native to Iran. The experiments were performed during two consecutive years (2014 and 2015). Combine analysis showed that there is no significant difference between the data of 2 years in all measured traits. High or very high levels of variations were detected in berry weight (0.14-1.30 g), antioxidant activity (40.21-88.08%), anthocyanin (80.74-145.09 mg/100 g), TSS (7.9-17.8 °Brix), TA (0.36-0.83%) and AA (9.56-20.92 mg/100 g). This is while TP showed very low levels of variation (109.5-129.1 mg/100 g). Correlation analysis showed that antioxidant activity correlated highly and positively with all of the measured characteristics including ascorbic acid (r = 0.927), anthocyanin (r = 0.752), total phenol (r = 0.681), TSS (r = 0.473) and berry weight (r = 0.541) except for TA. Cluster analysis based on all measured characteristics showed a partial differentiation between the accessions based on their species and, to lesser extent, according to their origin within the main clusters. Based on the bi-plot of the first two PCAs, genotypes and traits classified into four quadrants. This grouping was in agreement with that of cluster analysis, considering the fact that almost all of accessions in quadrants II and III (with a few exceptions) were same to those in the first clade of cluster analysis and the genotypes grouped in quadrants I and IV, represents the accessions of clade 2 in cluster analysis. The projection of the traits vectors in PCA were also fully in accordance to that of correlation analysis in almost all of studied traits. Results showed that a rich source of variations is available considering berry weight, fruit bio-chemical and antioxidant activity in the Iranian wild Rubus species, which needs immediate conservation and worth to be utilized in commercial breeding programs.