Exogenous γ-aminobutyric acid (GABA) enhances rye (Secale cereale) seedling resistance to combined freeze-thaw and cadmium stress.

Freeze-thaw is a common stress at high altitudes in northern China. There is a risk of cadmium (Cd) contamination in the region. γ-aminobutyric acid (GABA) is a natural product that regulates plant growth. Rye (Secale cereale ) was used as research material to investigate the physiological effects of exogenous GABA on rye seedlings under the single and combined stresses of freeze-thaw and cadmium. The results showed that the combined stress severely inhibited shoot length, root length, fresh weight, and dry weight, increased malondialdehyde and hydrogen peroxide contents, and significantly decreased superoxide dismutase (SOD) activity. Foliar application of 5mM GABA alleviated the negative effects of stress on seedling growth, increased soluble protein content, and reduced malondialdehyde and hydrogen peroxide contents. Exogenous GABA application also enhanced the activities of SOD and peroxidase (POD). Additionally, the presence of exogenous GABA activated the GABA metabolic process and encouraged the accumulation of phytochelatins, glutathione, and non-protein thiol. These results indicate that exogenous GABA can effectively improve the resistance of rye seedlings to freeze-thaw and Cd by regulating the antioxidant enzyme system and enhancing its own detoxification mechanism, and they provide a basis for future applications of exogenous GABA, which is beneficial for ecological protection.

Temperature adaptation patterns in Chinese cattle revealed by TRPM2 gene mutation analysis.

Cattle are sensitive to temperature fluctuations but adapt well to inclement weather conditions. When environmental temperatures exceed specific thresholds, heat stress becomes a critical concern for cattle. The TRPM2 gene, which resides on cattle chromosome 1 encodes a TRP channel protein, holding a unique capacity to sense temperature changes and facilitate rapid response to avoid heat stress. Here, we utilized the Bovine Genome Variation Database (BGVD) (http://animal.omics.pro/code/index.php/BosVar), and identified a missense mutation site, c.805A > G: p. Met269Val (rs527146862), within the TRPM2 gene. To elucidate the functional assessment of this mutation in temperature adaptation attributes of Chinese cattle, we genotyped 407 samples from 20 distinct breeds representing diverse climatic zones across China. The association analysis incorporates three temperature parameters and revealed compelling insights in terms of allele frequency. Interestingly, the prevalence of the wild-type allele A was notably higher among northern cattle breeds and this trend diminished gradually as observed in southern cattle populations. Conversely, the mutant-type allele G demonstrated a contrasting trend. Moreover, southern cattle exhibited markedly higher frequencies of GG and GA genotypes (P < 0.01). The presence of heterozygous and homozygous mutations appears to confer an enhanced capacity for adaptation to elevated temperatures. These results provide unequivocal correlation evidence between TRPM2 genotypes (AA, GA, GG) and environmental temperature parameters and comprehend the genetic mechanisms governing temperature adaptation in cattle. This provides valuable insights for strategic breed selection across diverse climatic regions, thereby aiding livestock production amid evolving climate challenges.

The TRPM2 gene encodes TRP channel protein that helps animals in combating heat stress. Twenty Chinese local cattle breeds were genotyped, and association analysis was performed. This investigation encompasses the distribution pattern of the missense mutation locus rs527146862 of the TRPM2 gene in southern, northern, and central cattle populations. The results demonstrated a significant relationship between rs527146862 locus and temperature adaptation attributes in Chinese cattle.

Artemisinin and Ambrosia trifida extract aggravate the effects of short freeze-thaw stress in winter rye (Secale cereale) seedlings.

The freeze-thaw and allelopathy from alien giant ragweed (Ambrosia trifida L.) and artemisinin have led to a serious stress to plants, influencing the agricultural quality and crop yield in north-east China. Yet, little is known how allelopathy affect plants under the freeze-thaw process. In this study, the characteristics in winter rye (Secale cereale L.) seedlings were investigated by laboratory simulation. The results showed that during the freezing process, application of artemisinin and A. trifida extract significantly increased the soluble protein content and accelerated lipid peroxidation, while they significantly inhibited antioxidant enzymes, photosynthesis and respiration (P <0.05). During the thawing process, the freezing pressure decreased, and activities of antioxidant enzymes were significantly improved to mitigate artemisinin and A. trifida extract induced stress (P <0.05). In addition, the sensitivity of the investigated metabolic processes in winter rye seedlings were highest to artemisinin and A. trifida extract in the freezing process. This study suggested that the stress response induced by artemisinin and A. trifida extract on winter rye seedlings in the freezing process was greater than that in the thawing process.

Impact of repeated freeze-thaw cycles environment on the allelopathic effect to Secale cereale L. seedlings.

Allelopathy, as environmental stress, plays a prominent role in stress ecotoxicity, and global warming directly increases freeze-thaw cycles (FTCs) frequency in the winter. Yet, the effect between FTCs environment and allelopathy stress is rarely known, and the interaction of allelopathy stresses lacks consideration. Here, we addressed interactions between artemisinin stress (AS) and A. trifida extract stress (AES) under Non-FTCs and FTCs environments. The results found that AS and AES had an antagonistic relation under Non-FTCs environment, while a strong synergism and cooperation under FTCs environment affect the growth and physiology in S. cereale seedlings. Besides, AS and AES under FTCs environment had more inhibition on the growth of roots and shoots, chlorophylls, photosynthetic parameters, and relative water content; while more promotion on malondialdehyde, soluble sugar, and soluble protein. Moreover, the antioxidant enzyme activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX) were increased by AS and AES, showing a good resistance of S. cereale seedlings to allelopathy stress, but FTCs environment significantly weakened this resistance. Thus, the allelopathic effect of AS and AES on S. cereale seedlings was significantly emphasized by FTCs environment.

Response characteristics of highland barley (Hordeum vulgare) seedlings to the stress of salinity and artemisinin under freeze­thaw environment.

In Qinghai-Tibet Plateau, crops are commonly subjected to freeze-thaw and salt stress factors simultaneously, and allelopathy is common, which affects the growth of highland barley (Hordeum vulgare L.), the largest food crop in Tibet. In order to explore the effects of artemisinin, salt and freeze-thaw (FAS) stress on physiological characteristics of highland barley seedlings, hydroponic experiment was carried out with the addition of 20mg/L artemisinin and 150mMNaCl as well as the simulation of freeze-thaw environment. The results suggested that under combined stress, the soluble protein content in combined stresses of artemisinin, FAS increased by 97.8%, the variation of relative conductivity in FAS group was lower than that in combined salt and freeze-thaw stress (FS), the relative water content decreased significantly (P <0.05), the malondialdehyde (MDA), H2 O2 and soluble sugar content in FAS group accumulated but less than those in FS group, and the superoxide dismutase (SOD) activity in combined artemisinin and freeze-thaw stress (FA) and FAS groups decreased. In addition, after freeze-thaw treatment, photosynthesis was weakened, and internal CO2 conentration (C i ) in FAS group significantly decreased (P <0.05). This study proved that appropriate amount of artemisinin can alleviate the damage of salt and freeze-thaw stress on barley seedlings.

[Effects of elevated carbon dioxide and ozone on the growth and secondary metabolism of spring wheat].

With open-top chamber (OTC), the effects of elevated CO2 (550 micromol x mol(-1)) and O3 (80 nmol x mol(-1)) and their combination on the biomass, total phenols, and flavone at different growth stages of spring wheat, as well as the yield components at maturity stage, were studied. The results showed that under elevated CO2, the biomass and yield components were significantly higher than those under ambient CO2 (342 micromol x mol(-1)), while under elevated O3, these parameters were significantly lower than those under ambient O3 (30 nmol x mol(-1)). The combination of elevated CO2 and O3 was at the intermediate place, indicating that CO2 could mitigate the negative effects of O3, while O3 could weaken the positive effects of CO2. Elevated CO2 and O3 increased the content of total phenols in wheat leaves, and the combination of elevated CO2 and O3 had the greatest effect. However, at late growth stage, the increment of total phenols was decreased. At early growth stage, the total content of leaf flavone under elevated CO2 and O3 and their combination was lower than the control, but at maturing stage, it was in adverse.

Effects of elevated CO(2) and O(3) on phenolic compounds in spring wheat and maize leaves.

C(3) crops are generally considered more sensitive than C(4) crops to the elevated CO(2) and O(3), but it is unclear whether the concentrations of phenolic compounds in them are affected. In this paper, an enrichment experiment with open-top chamber was conducted to examine the effects of elevated CO(2), O(3), and their combination on the contents of total phenolic compounds and flavone in the leaves of spring wheat (C(3) crop) and maize (C(4) crop). The results showed for spring wheat, the total phenolic contents in its leaves at jointing stage was significantly higher under elevated CO(2) and/or O(3), with the sequence of CO(2) plus O(3) > O(3) > CO(2) > ambient, while at grain-filling stage, the total phenolic content was lower under CO(2) plus O(3) than under CO(2), O(3), and ambient. The total phenolic content in maize leaves at jointing stage had the similar variation trend with that for wheat, but at grain-filling stage, the total phenolic content was slightly affected by elevated CO(2) and/or O(3). The flavone content in spring wheat leaves was significantly lower under CO(2) and/or O(3) stress at jointing stage, but had lesser difference at grain-filling stage under the stress. The same variation trend was observed in the flavone content in maize leaves at jointing and grainfilling stages, i.e., CO(2) plus O(3) > CO(2) > ambient > O(3). C(3) plant was more sensitive than C(4) plant to the CO(2) and/or O(3) stress.