Root Tolerance Research Articles

Functional responses to multiple sequential abiotic stress (waterlogging-drought) in three woody taxa with different root systems and stress tolerance.

There is generally a trade-off in the resistance to drought and to waterlogging. However, several species are sequentially subjected to both stressors in many environments. We evaluated the ecophysiological strategies to cope with multiple sequential stress of waterlogging and drought (W + D) of three taxa differing in stress resistance and root morphology: the phreatophic Eucalyptus camaldulensis (Ec) and two shallow-rooted willow clones: Salix matsudana x Salix alba (SmxSa) and Salix nigra (Sn4). Individuals of the three taxa were grown in pots and assigned to either of four treatments: Control (well-watered plants), well-watered followed by drought (C + D); waterlogged for 15 days followed by drought (W15d + D) and waterlogged for 30 days followed by drought (W30d + D). Biomass allocation, growth (diameter, height, length of leaves, and roots), specific leaf area, stomatal conductance, water potential, hydraulic conductivity of roots and branches, leaf C13 and root cortical aerenchyma formation were determined at different stages of the experiment. Ec growth was not affected by W + D, developing tolerance strategies at leaf and whole plant levels. Differential effects of W + D were observed in both Salix clones depending on the time of waterlogging. In Sn4 and SmxSa, the root biomass was affected in W15d + D treatment, but a root tolerance response (aerenchyma and adventitious root formation) was observed in W30d + D. In the three taxa, and contrary to expectations, the previous exposure to a waterlogging period did not increase the susceptibility of the plants to a subsequent drought event. On the contrary, we found tolerance, which depended on the time of waterlogging exposure.

The Effects of Coexisting Elements (Zn and Ni) on Cd Accumulation and Rhizosphere Bacterial Community in the Soil-Tomato System

The increasing cadmium (Cd) levels in agricultural soils have become a worldwide concern for food crop security. Cd accumulation in the soil-plant system is closely related to other coexisting factors. In this study, the effects of different levels of Zn or Ni on Cd accumulation in tomato plants and on the rhizosphere soil bacterial community structure were analyzed by coupling pot experiments with high-throughput sequencing. The results demonstrated that tomato plants (Lycopersicon esculentum) in Zn-Cd and Ni-Cd co-contaminated soils exhibited lower relative growth rates. Co-contamination at low levels tended to reduce the bioaccumulation of heavy metals in the roots of plants, whereas increased contaminant concentrations produced the opposite effect. In the presence of 200 mg/kg Zn or 20 mg/kg Ni, the biomass of plant roots increased by 4.95–23.16% and the Cd content of the plant roots decreased by 17.36–68.93% due to the antagonistic effects between Cd and Zn/Ni. In addition, the richness and diversity of the bacterial community were significantly altered under HMs co-contamination, and the number of special bacteria was positively correlated with the level of heavy metals in the rhizosphere soil. The relative abundance of Proteobacteria increased and that of Actinobacteria decreased in soils with low levels of heavy metals. This may improve the tolerance of plant roots to heavy metals and reduce the accumulation of Cd in plant roots. These findings highlight the important role of coexisting elements in the inhibition of Cd accumulation in tomatoes and offer important information for the production of safe crops.

Integrative transcriptome and metabolome analysis reveals the mechanism of exogenous melatonin alleviating drought stress in maize roots

Melatonin (MT) is essential for plant development and drought adaptation. However, the molecular and metabolic mechanisms underlying MT-induced drought tolerance in maize roots remain largely unclear. Herein, we investigated the effects of MT on drought tolerance in maize roots using integrated transcriptomic and metabolomic analyses, and identified MT-induced genes and metabolites associated with drought resistance. Compared with the untreated control plants, MT application alleviated the deleterious effects of drought on roots, by decreasing the malondialdehyde level and increasing the solute potential, eventually promoting root growth. Transcriptome and metabolome analysis demonstrated that MT significantly upregulates the expression of genes related to flavonoid biosynthesis (PAL, C4H, 4CL, HCT, CHS, CHI, F3′5′H, and DFR), activates drought-responsive transcription factors (ERFs, NACs, MYBs, and bHLHs), and regulates hormone signaling-related genes, especially ethylene response factors (ERF4, ERF81, and ERF110). Moreover, MT increased the accumulation of flavonoid metabolites, particularly apigenin, luteolin, and quercetin, under drought-stress conditions. These findings were further supported by quantitative real-time polymerase chain reaction analysis and total flavonoid measurements. Altogether, our findings suggest that MT promotes maize root growth during drought by regulating flavonoid synthesis pathways, transcription factors, and plant hormone signals. This study provides new insights into the complex mechanisms by which MT enhances crop resistance to drought damage.

Comparative transcriptome analysis of salt tolerance of roots in diploid and autotetraploid citrus rootstock (C. junos cv. Ziyang xiangcheng) and identification of salt tolerance-related genes

Polyploidization is a widespread phenomenon in flowering plants, and it often enhances abiotic stress tolerance. However, the related molecular mechanism remains largely unknown, especially for perennial woody plants. Here, we found that autotetraploid citrus (Citrus junos Sieb. ex Tanaka) had greater salt tolerance than their diploid progenitors. Transcriptome analysis identified a large number of differentially expressed genes (DEGs) between autotetraploid and diploid roots under salt stress. GO analysis showed that chitin response-related genes were enriched in roots of autotetraploid. Consistently, the autotetraploids exhibited higher chitinases activity than the diploids under salt stress. The top five transcription factor (TF) families with the largest number of TFs were bHLH, ERF, MYB, NAC, and WRKY in autotetraploids and diploids, and 25 TFs were higher expressed in autotetraploids than in diploids under salt stress. Our results revealed that salt stress induced the activation of chitin pathway, thus reducing in ROS accumulation, eventually enhancing salt tolerance of autotetraploid citrus. Our research provides the theoretical basis for citrus breeding aiming at abiotic stress tolerance enhancement.

SUMO protease GmOTSa positively regulates drought tolerance in transgenic tobacco and soybean hairy roots

SUMO protease is important for regulating the balance of SUMOylation and deSUMOylation. Despite the investigations of several SUMO protease genes in model plants, to date, the biological functions of these regulatory enzymes in soybean have yet to be ascertained. In the present study, a SUMO protease GmOTSa was identified in soybean, and was localized in the nucleus with the bona fide SUMO protease activity both in vitro and in vivo. Further RTqPCR analysis showed that GmOTSa was expressed in various tissues and was highly induced by PEG treatment. We demonstrated that GmOTSa conferred drought tolerance in tobacco plants by increasing the germination rate, the fresh and dry weights upon water deficit, and improving the survival rate after rewatering. Overexpression of GmOTSa gene in tobacco lines and soybean hairy roots enhanced drought tolerance by positively regulating ROS scavenging, thus maintained lower ROS content. Moreover, less MDA content and higher total chlorophyll content as well as promoted closure of stomata were detected in the OE plants than in the WT plants in response to drought stress. Conversely, soybean hairy roots with simultaneous knockout of GmOTSa and the homologous gene GmOTSb using the CRISPRCas9 method exhibited reduced drought tolerance. Correspondingly, the expression of drought-related genes showed greater induction upon drought stress in the GmOTSa-overexpressed lines. Overall, these results indicated that GmOTSa may act as a positive regulator of drought responses and therefore could be considered a potential gene for the genetic improvement of drought tolerance.

Root frost tolerance, seasonal variation in root growth, and field performance of one-year-old Russian larch seedlings with simulated root freezing damages

ABSTRACT Planting healthy seedlings with optimal growth potential is essential for proper growth and survival in forest regeneration. Assessing the seedling quality prior to planting is therefore important. In this Icelandic study, effects of root damage induced with artificial freezing in young Russian larch seedlings were examined using the root growth capacity method (RGC). Frost tolerance of roots varied during the winter, and root growth in undamaged seedlings fluctuated, indicating seasonal variations in growth rhythm. The LT50 value for root frost tolerance was −13.9°C in late January, but already at −10.6°C (LT10) root damages were severe. After one growing season, shoot elongation was significantly lower in seedlings frozen to −9°C, −13.5°C, and −15.5°C by 23%, 54%, and 72%, respectively, compared with undamaged seedlings. Control seedlings and seedlings frozen to −9°C achieved 100% survival after the first growing season. Survival in seedlings frozen to −13.5°C and −15.5°C was 85% and 27%, respectively. After the second growing season, survival decreased in all frost-damaged seedlings. The ongoing mortality demonstrates the long-lasting effects of planting seedlings with damaged root systems, and the fluctuation in root frost tolerance of young Russian larch seedlings during winter emphasises the need for care when seedlings are moved to outdoor storage.

Rapid screening of pea (Pisum sativum) genotypes against aluminium toxicity

Twenty-five pea genotypes were grown in trays under a controlled environment in the laboratory of Basic Sciences and Humanities, College of Horticulture and Forestry, CAU, Pasighat, Arunachal Pradesh (2018–2021) and evaluated at 3 levels of Al (0 ppm, 12 ppm and 24 ppm). Al treatment was given through Hoagland solution. Screening of pea genotypes was performed using growth characters, root tolerance index and haematoxylin staining. The genotypes Kashi Samridhi, CHFGP-1 and CHFGP‑14 exhibited an increase in root and shoot biomass. Nearly all the genotypes exhibited reduction in root and shoot length. Based on the K-clustering score P.S.M.3, Kashi Samrath, Kashi Samridhi, CHFGP-1, CHFGP-7 and CHFGP-55 were observed as tolerant at 24 ppm Al level. Matar Ageta-7, Pb-89, AP-3, Pusa Pragati, Arka Priya, Kashi Shakti, CHFGP-6, VRPE- 29, NO-17 and CHFGP-15 were categorized as susceptible genotypes.a

Comparative Transcriptome Analysis of Salt-Stress-Responsive Genes in Rice Roots

Soil salinity greatly impairs plant growth and crop productivity. Rice (Oryza sativa L.) is a salt-sensitive crop. To better understand the molecular mechanisms of salt tolerance in roots, the BGISEQ-500 sequencing platform was employed to elucidate transcriptome changes in rice roots after 0, 3, 24, and 72 h of salt stress. The results showed that root K+ content decreased and Na+ content increased rapidly after the initial stage of salt stress, but that fresh and dry weight in root did not significantly reduce. Compared to the control (no salt stress), 1,292, 453, and 486 differentially expressed genes (DEGs) were upregulated, respectively, and 939, 894, and 646 DEGs were downregulated, respectively, after 3, 24, and 72 h of salt treatment. The number of DEGs was higher during the early stage of salt stress (3 h) than in later stages (24 and 72 h). A number of DEGs involved in the response and adaptation to salt stress were related to protein kinase and calcium-binding, plant hormone signaling and metabolism, transcriptional regulation, metabolic pathways, antioxidant activity, and ion transport. Many of these DEGs were activated during the early stage of salt stress (3 h). The present study reports candidate salt-stressresponsive genes with the potential to genetically improve salt tolerance in rice elsewhere.

Metal tolerance capacity and antioxidant responses of new Salix spp. clones in a combined Cd-Pb polluted system.

To investigate the physiochemical characteristics of two new clones, Salix matsudana 'J172' (A7) and Salix matsudana 'Yankang1' (A64) in combined Cd-Pb contaminated systems, a hydroponic experiment was designed. The plant biomass, photosynthesis, antioxidant responses and the accumulation of metals in different plant parts (leaf, stem, and root) were measured after 35-day treatments with Cd (15, 30 µM) and Pb (250, 500 µM). The results showed that exposure to Cd-Pb decreased the biomass but increased the net photosynthetic rate for both A7 and A64, demonstrating that photosynthesis may be one of the metabolic processes used to resist Cd-Pb stress. Compared with control, roots exposed to Cd-Pb had higher activity of superoxide dismutase and more malondialdehyde concentrations, which indicated the roots of both clones were apt to be damaged. The concentrations of soluble protein were obviously higher in the roots of A64 than A7, indicating the roles of the antioxidative substance were different between two willow clones. Soluble protein also had significant relationship with translocation factors from accumulation in roots of A64, which illustrated it played important roles in the tolerance of A64 roots to heavy metals. The roots could accumulate more Pb rather than transport to the shoots compared with Cd. The tolerance index was more than 85% on average for both clones under all the treatments, indicating their tolerance capacities to the combined stress of Cd and Pb are strong under the tested metal levels. Both clones are the good candidates for phytoremediation of Cd and Pb by the root filtration in the combined contamination environment.

Elimination of root kissing bond in friction stir welding of thick plates

• The root-enhanced friction stir welding was proposed to eliminate root kissing bond. • The root tolerance had been expanded from 0.1 mm to 0.6 mm. • The enlarged-tip pin increased heat input and material deformation at the bottom. • The tensile properties were increased to 345 MPa. Root kissing bond in thick-plate friction stir welded joints limits the application of plates in fuel tanks of heavy launch vehicles. Here a root-enhanced friction stir welding from aspects of the on-demand distribution of heat input and plastic deformation through an enlarged-tip pin was proposed. The pin was designed with an enlarged tip for enhanced plasticizing and forging on root materials. Root tolerance, defined by the distance between the pin tip and the lower surface of the plate without a root kissing bond, was proposed to evaluate the feasibility of the designed pin. This value increased from 0.1 mm to 0.6 mm compared to the conventional conical pin. The ultimate tensile strength and elongation reached 345±4 MPa and 11.8±0.7%, which were 11.3% and 87.3% higher than the joint by the conical pin.

Physiological and molecular responses of roots differ from those of leaves in spinach plants subjected to short-term drought stress

• Physiological and molecular responses of roots differ from those of leaves in spinach plants subjected to short-term drought stress. • Short-term drought stress triggers oxidative stress in roots but not in leaves. • Dehydrin and PLDα1 polypeptides with different molecular weights accumulate in roots and leaves. • Drought tolerance of roots and leaves might be associated with expression profiles of Dehydrin and PLDα1 polypeptides in these tissues. In this study, physiological responses as well as changes in expressions of specific proteins (dehydrin [DHN] and phospholipase Dα1 [PLDα1]) were determined in leaf and root tissues of Spinacia oleracea L.cv. Matador plants under different levels of drought stress. Spinach plants grown in the plant growth chamber were exposed to two levels of drought stress (Moderate Stress [MS]: 50% Field Capacity [FC] and Severe Stress [SS]: 25% FC) and compared with no stress conditions (Control: 100% [FC]) for a period of 10 days. Results revealed that the roots and leaves of spinach plants responded differently to drought stress, probably due to different antioxidant activities and accumulation of specific proteins (DHN and PLDα1). Moderate or severe drought stress did not alter the oxidation parameters in leaves of S. oleracea L. cv. Matador plants while significant changes associated with oxidative stress were observed in roots. Dehydrin polypeptides (75 and 50 kDa for leaves and 75 kDa for roots) and PLDα1 polypeptides (22 kDa in leaves; 52 kDa and 28 kDa in roots) have been observed to accumulate following drought exposure. The accumulation of these polypeptides was associated with physiological responses of spinach plants which provide evidence for their contribution to the acclimation process in early drought stress. These data suggest that tissues of spinach plant respond differently against different levels of drought stress and that the response is associated with altered expressions of DHN and PLDα1 polypeptides.

Regulation of salt tolerance in the roots of Zea mays by L-histidine through transcriptome analysis.

Soil salinization is an important worldwide environmental problem and the main reason to reduce agricultural productivity. Recent findings suggested that histidine is a crucial residue that influences the ROS reduction and improves the plants' tolerance to salt stress. Herein, we conducted experiments to understand the underlying regulatory effects of histidine on maize root system under salt stress (100 mM NaCl solution system). Several antioxidant enzymes were determined. The related expressed genes (DEGs) with its pathways were observed by Transcriptome technologies. The results of the present study confirmed that histidine can ameliorate the adverse effects of salt stress on maize root growth. When the maize roots exposed to 100 mM NaCl were treated with histidine, the accumulation of superoxide anion radicals, hydrogen peroxide, and malondialdehyde, and the content of nitrate nitrogen and ammonium nitrogen were significantly reduced; while the activities of superoxide dismutase, peroxidase, catalase, nitrate reductase, glutamine synthetase, and glutamate synthase were significantly increased. Transcriptome analysis revealed that a total of 454 (65 up-regulated and 389 down-regulated) and 348 (293 up-regulated and 55 down-regulated) DEGs were observed when the roots under salt stress were treated with histidine for 12 h and 24 h, respectively. The pathways analysis of those DEGs showed that a small number of down-regulated genes were enriched in phytohormone signaling and phenylpropanoid biosynthesis at 12 h after histidine treatment, and the DEGs involved in the phytohormone signaling, glycolysis, and nitrogen metabolism were significantly enriched at 24 h after treatment. These results of gene expression and enzyme activities suggested that histidine can improve the salt tolerance of maize roots by enriching some DEGs involved in plant hormone signal transduction, glycolysis, and nitrogen metabolism pathways.

Effect of Nickel Ions on the Physiological and Transcriptional Responses to Carbon and Nitrogen Metabolism in Tomato Roots under Low Nitrogen Levels.

Nickel (Ni) is an essential trace element for plant growth and a component of the plant body that has many different functions in plants. Although it has been confirmed that nickel ions (Ni2+) havea certain regulatory effect on nitrogen (N) metabolism, there are not enough data to prove whether exogenous Ni2+ can increase the carbon (C) and N metabolism in the roots of tomato seedlingsunder low-nitrogen (LN) conditions. Therefore, through the present experiment, we revealed the key mechanism of Ni2+-mediated tomato root tolerance to LN levels. Tomato plants were cultured at two different N levels (7.66 and 0.383 mmol L−1) and two different Ni2+ levels (0 and 0.1 mg L−1 NiSO4 6H2O) under hydroponic conditions. After nine days, we collected roots for physiological, biochemical, and transcriptome sequencing analyses and found that the activities of N assimilation-related enzymes decreased at LN levels. In contrast, Ni2+ significantly increased the activities of N assimilation-related enzymes and increased the contents of nitrate (NO3−), ammonium (NH4+), and total amino acids. Through root transcriptomic analysis, 3738 differentially expressed genes (DEGs) were identified. DEGs related to C and N metabolism were downregulated after LN application. However, after Ni2+ treatment, PK, PDHB, GAPDH, NR, NiR, GS, GOGAT, and other DEGs related to C and N metabolism were significantly upregulated. In conclusion, our results suggest that Ni2+ can regulate the C and N metabolism pathways in tomato roots to alleviate the impact of LN levels.

OsABT Is Involved in Abscisic Acid Signaling Pathway and Salt Tolerance of Roots at the Rice Seedling Stage.

Rice is a staple cereal crop worldwide, and increasing its yields is vital to ensuring global food security. Salinity is a major factor that affects rice yield. Therefore, it is necessary to investigate salt tolerance mechanisms in rice. Proteins containing WD40 repeats play important roles in eukaryotic development and environmental adaptation. Here, we showed that overexpression of OsABT, a gene encoding a WD40-repeat protein, enhanced salt tolerance in rice seedlings by regulating root activity, relative conductivity, malondialdehyde and H2O2 content, and O2•− production rate. Root ion concentrations indicated that OsABT overexpression lines could maintain lower Na+ and higher K+/Na+ ratios and upregulated expression of salt-related genes OsSOS1 and OsHAK5 compared with the wild-type (WT) Nipponbare plants. Furthermore, Overexpression of OsABT decreased the abscisic acid (ABA) content, while downregulating the ABA synthesis genes OsNCED3 and OsNCED4 and upregulating the ABA catabolic gene OsABA8ox2. The yeast two-hybrid and bimolecular fluorescence complementation analyses showed that OsABT interacted with the ABA receptor proteins OsPYL4, OsPYL10, and PP2C phosphatase OsABIL2. A transcriptome analysis revealed that the differentially expressed genes between OsABT overexpression lines and WT plants were enriched in plant hormone signal transduction, including ABA signaling pathway under salt stress. Thus, OsABT can improve the salt tolerance in rice seedling roots by inhibiting reactive oxygen species accumulation, thereby regulating the intracellular Na+/K+ balance, ABA content, and ABA signaling pathway.

Exogenous silicon enhances resistance to 1,2,4-trichlorobenzene in rice

Environmental contamination with 1,2,4-trichlorobenzene (TCB) is a threat to rice growth, and ultimately, to human health. Silicon (Si) plays an important role in plants' stress responses. However, little is known about the effects of Si on the TCB tolerance of rice plants. We investigated the effects of Si on the morphological, physiological, and molecular characteristics of rice plants under TCB stress. First, we compared the TCB tolerance of 13 rice cultivars by measuring seven growth-related and 13 physiological indices across four treatments. Then, six cultivars with contrasting TCB tolerance were selected to study the expression of Si transport and detoxification related genes. Compared with the control, the TCB treatment resulted in decreased growth indices, chlorophyll content, and antioxidant enzyme activities, and increased the superoxide anion content and root electrical conductivity. Application of Si improved rice growth, chlorophyll content and alleviated oxidative damage caused by TCB. The alleviating effect of Si ranged from 4.1 % to 56.72 % among the cultivars, with the strongest alleviating effect on Wuyujing 36. The transcript levels of genes encoding Si transporters and detoxification enzymes were higher in tolerant cultivars than in sensitive cultivars. The TCB treatment induced the expression of GST and Lsi2 in roots and HO-1 in leaves; these genes as well as Lsi1 were differentially expressed in roots and/or leaves in the TCB + Si treatment. Lsi1 played a key role in Si-mediated TCB tolerance in Wuyujing 36. The joint analysis of gene transcript levels in TCB and TCB + Si treatments confirmed that all six genes were associated with TCB tolerance, especially Lsi1 and Lsi2 in roots and GST and CuZn-SOD in leaves. Si can increase rice plants' resistance to TCB stress by improving growth and enhancing superoxide dismutase (SOD) activity and chlorophyll content, and by up-regulating genes involved in Si transport and detoxification.

CBL-Interacting Protein Kinase 2 Improves Salt Tolerance in Soybean (Glycine max L.)

Salt stress severely limits soybean production worldwide. Calcineurin B-like protein-interacting protein kinases (CIPKs) play a pivotal role in a plant’s adaption to salt stress. However, their biological roles in soybean adaption to salt stress remain poorly understood. Here, the GmCIPK2 expression was increased by NaCl and hydrogen peroxide (H2O2). GmCIPK2-overexpression Arabidopsis and soybean hairy roots displayed improved salt tolerance, whereas the RNA interference of hairy roots exhibited enhanced salt sensitivity. Further analyses demonstrated that, upon salt stress, GmCIPK2 enhanced the proline content and antioxidant enzyme activity and decreased the H2O2 content, malondialdehyde (MDA) content, and Na+/K+ ratios in soybean. Moreover, GmCIPK2 promoted the expression of salt- and antioxidant-related genes in response to salt stress. Moreover, the GmCIPK2-interacting sensor, GmCBL4, increased the salt tolerance of soybean hairy roots. Overall, these results suggest that GmCIPK2 functions positively in soybean adaption to salt stress.

Systematic Analysis of bHLH Transcription Factors in Cassava Uncovers Their Roles in Postharvest Physiological Deterioration and Cyanogenic Glycosides Biosynthesis.

The basic helix-loop-helix (bHLH) proteins are a large superfamily of transcription factors, and play a central role in a wide range of metabolic, physiological, and developmental processes in higher organisms. However, systematic investigation of bHLH gene family in cassava (Manihot esculenta Crantz) has not been reported. In the present study, we performed a genome-wide survey and identified 148 MebHLHs genes were unevenly harbored in 18 chromosomes. Through phylogenetic analyses along with Arabidopsis counterparts, these MebHLHs genes were divided into 19 groups, and each gene contains a similar structure and conserved motifs. Moreover, many cis-acting regulatory elements related to various defense and stress responses showed in MebHLH genes. Interestingly, transcriptome data analyses unveiled 117 MebHLH genes during postharvest physiological deterioration (PPD) process of cassava tuberous roots, while 65 MebHLH genes showed significantly change. Meanwhile, the relative quantitative analysis of 15 MebHLH genes demonstrated that they were sensitive to PPD, suggesting they may involve in PPD process regulation. Cyanogenic glucosides (CGs) biosynthesis during PPD process was increased, silencing of MebHLH72 and MebHLH114 showed that linamarin content was significantly decreased in the leaves. To summarize, the genome-wide identification and expression profiling of MebHLH candidates pave a new avenue for uderstanding their function in PPD and CGs biosynthesis, which will accelerate the improvement of PPD tolerance and decrease CGs content in cassava tuberous roots.

Tolerance response of varied tomato genotypes grown at excess manganese (Mn)

Abstract. Zahara S, Carsono N, Sudirja R, Soleh MA. 2022. Tolerance response of varied tomato genotypes grown at excess manganese (Mn). Biodiversitas 23: 3209-3218. High Mn concentration in acidic soil has been known as a limiting factor of sustainable tomato production. In addition, the number of tomato cultivars available to be grown under such conditions is still limited. Therefore, this study tested the Mn tolerance response among four tomato genotypes, Opal, Mutiara, Ratna, and Mirah, grown hydroponically. Nutrient solutions were added to Mn for concentrations of 0, 50, 100, and 200 ppm. The increase of Mn concentration ([Mn]) significantly decreased chlorophyll fluorescence and stomatal conductance. Shoot Tolerance Index (STI) and Root Tolerance Index (RTI) among genotypes were significant differences in response to Mn concentration. Genotype Mirah was the lowest Mn accumulation in the shoot and root compared to other genotypes. Most of the Mn absorbed by Mirah was accumulated in the roots. The tolerance ranks of the tomato genotype tested for Mn toxicity were Mirah > Opal > Ratna > Mutiara. This indicates that genetic composition plays an essential role in Mn tolerance. The tolerance response of Mirah was due to its ability to prevent Mn from being absorbed by the shoot, which led to the effect of shoot toxicity. This response might help improve tomato genotypes tolerance under high Mn soil.

The soybean PLATZ transcription factor GmPLATZ17 suppresses drought tolerance by interfering with stress-associated gene regulation of GmDREB5

Plant AT-rich sequence and zinc binding (PLATZ) transcription factors are a class of plant specific zinc-dependent DNA-binding proteins that function in abiotic stress response and plant development. In this study, 31 GmPLATZ genes were identified in soybean. GmPLATZ17 was down-regulated by drought and exogenous abscisic acid. Transgenic Arabidopsis and soybean hairy roots overexpressing GmPLATZ17 showed drought sensitivity and inhibition of stress-associated gene transcription. In contrast, suppressed expression of GmPLATZ17 led to increased drought tolerance in transgenic soybean hairy roots. The GmPLATZ17 protein was verified to interact physically with the GmDREB5 transcription factor, and overexpression of GmDREB5 increased drought tolerance in soybean hairy roots. Interaction of GmPLATZ17 with GmDREB5 was shown to interfere with the DRE-binding activity of GmDREB5, suppressing downstream stress-associated gene expression. These results show that GmPLATZ17 inhibits drought tolerance by interacting with GmDREB5. This study sheds light on PLATZ transcription factors and the function of GmPLATZ17 in regulating drought sensitivity.

Mitigation of chilling injury in sweet potato roots subjected to low-temperature conditioning

In many plant tissues, low-temperature conditioning (LTC) has been used to induce postharvest adaptive responses to overcome chilling injury (CI) consequences. This study aimed to investigate whether LTC is effective in reducing the incidence of chilling injury (CI) in sweet potato cultivars. Sweet potato roots BRS Cuia and BRS Rubissol were submitted to cold storage (6 °C or 13 °C) and LTC (10 °C for 7 d, followed by second storage at 6 °C). LTC increased the tolerance of sweet potato roots to CI via antioxidant system activation, mainly in cv. BRS Rubissol, which was markedly associated with higher content of both total soluble phenolics and proline, as well as increased activity of phenylalanine ammonium lyase. Moreover, no either external or internal injuries were observed in the LTC roots, maintaining the quality for processing, which indicates that the LTC is effective in mitigating chilling injury in Brazilian sweet potato cultiva