Cloning and Functional Study of AmGDSL1 in Agropyron mongolicum.

Agropyron mongolicum Keng is a diploid perennial grass of triticeae in gramineae. It has strong drought resistance and developed roots that can effectively fix the soil and prevent soil erosion. GDSL lipase or esterases/lipase has a variety of functions, mainly focusing on plant abiotic stress response. In this study, a GDSL gene from A. mongolicum, designated as AmGDSL1, was successfully cloned and isolated. The subcellular localization of the AmGDSL1 gene (pCAMBIA1302-AmGDSL1-EGFP) results showed that the AmGDSL1 protein of A. mongolicum was only localized in the cytoplasm. When transferred into tobacco (Nicotiana benthamiana), the heterologous expression of AmGDSL1 led to enhanced drought tolerance. Under drought stress, AmGDSL1 overexpressing plants showed fewer wilting leaves, longer roots, and larger root surface area. These overexpression lines possessed higher superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and proline (PRO) activities. At the same time, the malondialdehyde (MDA) content was lower than that in wild-type (WT) tobacco. These findings shed light on the molecular mechanisms involved in the GDSL gene's role in drought resistance, contributing to the discovery and utilization of drought-resistant genes in A. mongolicum for enhancing crop drought resistance.

Variations in Cadmium and Lead Bioaccessibility in Wheat Cultivars and Their Correlations with Nutrient Components.

To reduce the health risks of exposure to Cd and Pb in wheat, a field experiment was conducted to investigate the differences in Cd and Pb bioaccessibility among the grains of 11 wheat cultivars and their relationships with the nutrient compositions of grains. The grain concentrations (Cd: 0.14-0.56 mg kg-1, Pb: 0.08-0.39 mg kg-1) and bioaccessibility (5.28-57.43% and 0.72-7.72% for Cd and Pb in the intestinal phase, respectively) of Cd and Pb differed significantly among the 11 cultivars. A safe wheat cultivar (Shannong16) with a relatively low health risk and the lowest grain Cd and Pb concentrations was selected. Ca, Mg, phytate, and methionine played key roles in affecting Cd and Pb bioaccessibility in wheat, with Ca and phytate significantly negatively correlated with Cd and Pb bioaccessibility. These findings can be used to optimize the selection strategy for safe wheat cultivars for healthy grain production in Cd-polluted farmland.

Photochemical degradation in natural attenuation of characteristics of petroleum hydrocarbons (C10-C40) in crude oil polluted soil by simulated long term solar irradiation.

Photodegradation process plays an important role in the natural attenuation of petroleum hydrocarbons (PHs) in oil contaminated soil. The photodegradation characteristics of PHs (C10-C40) in topsoil of crude oil contaminated soil irradiated by simulated sunlight in 280 d without microbial action were investigated. The results showed that photodegradation rate of PHs was increased with increasing the light intensity and decreased with increasing the initial concentration of PHs. Moreover, the photodegradation capacity of tested PHs was relevant to the length of carbon chain. The photodegradation rates of C10-C20 were higher than that of C21-C40 in photoperiod. C21-C40 showed an obvious trend of photodegradation after 56 d, although their photodegradation rates were less than 20% at the early stage. And, the redundancy analysis indicated that lighting time was the primary factor for photodegradation of PHs under abiotic conditions. The photodegradation rate was well interpreted by a two-stage, first-order kinetic law with a faster initial photolysis rate. The EPR spectrums showed that simulated solar irradiation accelerated the generation of superoxide radicals, which could react with PHs in soil. Also, the function groups in PHs polluted soil were changed after light exposure, which might imply the possible photodegradation pathway of PHs.

[Effects of Intercropping of Brassica chinenesis L. and Tagetes patula L. on the Growth and Cadmium Accumulation of Plants].

A pot experiment was conducted to reveal the effects of intercropping a low-cadmium (Cd) accumulating cultivar and a Cd hyperaccumulator on the safe utilization and phytoextraction of Cd-polluted soils. Two cultivars of Brassica chinensis L. (the low-Cd accumulating cultivar Huajun, and the common cultivar Hanlü), were intercropped with four cultivars of Tagetes patula L. (Dwarf Red, Dwarf Yellow, Tall Red, and Tall Yellow). We examined the biomass, photosynthetic characteristics, and Cd accumulation in the plants and available Cd content and dissolved organic carbon (DOC) content in the soils. The results show that under the intercropping treatments, the biomass of B. chinensis decreased significantly and those of T. patula increased significantly, compared with the monoculture treatments. When intercropped with T. patula, the net photosynthetic rate, stomatal conductance, and transpiration rate in the leaves of B. chinensis decreased significantly, compared with the monoculture treatments. When Huajun was intercropped with Dwarf Red, the shoot Cd content of Huajun significantly decreased by 14.5%, and that of Dwarf Red increased significantly by 36.5% compared with the monoculture. Under the other intercropping treatments, the shoot Cd content of B. chinensis increased significantly, or showed no significant change, and that of T. patula showed no significant change. Under the intercropping treatments, the total amount of Cd in the shoot of B. chinensis decreased significantly, and that of T. patula increased significantly, compared with the monoculture. There were no significant differences in the Cd extraction ratios between the intercropping treatments and the monoculture of T. patula. The shoot Cd content of B. chinensis was significantly correlated with soil available Cd content and DOC content (P<0.01 and P<0.05, respectively). In conclusion, the intercropping treatment of Huajun and Dwarf Red significantly reduced shoot Cd content in B. chinensis and increased that in T. patula, and it did not affect the Cd extraction ratio. This is suitable for the safe utilization and phytoextraction of Cd-polluted soils.

Pivotal role for root cell wall polysaccharides in cultivar-dependent cadmium accumulation in Brassica chinensis L.

Polysaccharides are the main components of plant cell walls in which they make an important contribution to cadmium (Cd) fixation. However, knowledge regarding the role of root cell wall polysaccharides in Cd accumulation in low-Cd cultivars is limited. Here, we compared the differences in root cell wall polysaccharides between two cultivars of Brassica chinensis L. (pakchoi) with different Cd accumulation abilities. A hydroponic experiment was conducted using low- (Huajun 2) and high-Cd (Hanlv) pakchoi cultivars. We investigated Cd subcellular distribution and Cd accumulation in cell wall polysaccharides and examined polysaccharide modifications in root cell walls by Fourier transform infrared spectroscopy. A Cd adsorption kinetics experiment was conducted to examine the connection between Cd-induced polysaccharide modifications and Cd fixation by cell walls. Amounts of Cd were significantly higher and more Cd was bound to cell walls in the roots of Huajun 2 than in those of Hanlv. These results indicated that the greater Cd retention capacity of the root cell wall in Huajun 2 accounted for the low Cd accumulation in the shoot. Up to 79.4% and 32.1% of cell-wall-bound Cd was found in the pectin and hemicellulose 1, respectively, and higher amounts of Cd were found in these cell wall components of Huajun 2 than in those of Hanlv. Exposure to Cd significantly increased amounts of pectin and hemicellulose 1 in both pakchoi cultivars, but the pectin levels were significantly higher in Huajun 2 than in Hanlv. Huajun 2 had higher pectin methylesterase (PME) activity and a lower degree of pectin methyl-esterification (DM) than Hanlv, although Cd treatments resulted in increased PME activity and decreased DM in both cultivars. The higher Cd treatment (44.5 µM) resulted in enhanced Cd-binding capacity in root cell walls of the two cultivars with higher Cd adsorption levels in the root cell wall of Huajun 2. These results indicate that differences in the amount of cell wall polysaccharide and DM play key roles in establishing the genotypic differences underlying Cd accumulation in pakchoi. These findings conduce to a better understanding of the physiological mechanisms underlying low Cd accumulation in pakchoi and the breeding of new, low-Cd pakchoi cultivars.