Variety-Driven Effect of Rhizosphere Microbial-Specific Recruitment on Drought Tolerance of Medicago ruthenica (L.)

As one of the environmental factors that seriously affect plant growth and crop production, drought requires an efficient but environmentally neutral approach to mitigate its harm to plants. Soil microbiomes can interact with plants and soil to improve the adverse effects of drought. Medicago ruthenica (L.) is an excellent legume forage with strong drought tolerance, but the key role of microbes in fighting drought stress remains unclear. What kind of flora plays a key role? Is the recruitment of such flora related to its genotype? Therefore, we selected three varieties of M. ruthenica (L.) for drought treatment, analyzed their growth and development as well as their physiological and biochemical characteristics, and performed 16S rRNA high-throughput sequencing analysis on their rhizosphere soils to clarify the variety-mediated response of rhizosphere bacteria to drought stress. It was found that among the three varieties of M. ruthenica (L.), Mengnong No.2, Mengnong No.1 and Zhilixing were subjected to drought stress and showed a reduction in plant height increment of 24.86%, 34.37%, and 31.97% and in fresh weight of 39.19%, 50.22%, and 41.12%, respectively, whereas dry weight was reduced by 23.26%, 26.10%, and 24.49%, respectively. At the same time, we found that the rhizosphere microbial community of Mengnong No. 2 was also less affected by drought, and it was able to maintain the diversity of rhizosphere soil microflora stable after drought stress, while Mennong No. 1 and Zhilixing were affected by drought stress, resulting in a decrease in rhizosphere soil bacterial community diversity indices to 92.92% and 82.27%, respectively. Moreover, the rhizosphere of Mengnon No. 2 was enriched with more nitrogen-fixing bacteria Rhizobium than the other two varieties of M. ruthenica (L.), which made it still have a good ability to accumulate aboveground biomass after drought stress. In conclusion, this study proves that the enrichment process of bacteria is closely related to plant genotype, and different varieties enrich different types of bacteria in the rhizosphere to help them adapt to drought stress, and the respective effects are quite different. Our results provide new evidence for the study of bacteria to improve the tolerance of plants to drought stress and lay a foundation for the screening and study mechanism of drought-tolerant bacteria in the future.

Quality Evaluation of Walnuts from Different Regions in China

This study analyzed and evaluated the basic crude fat contents, crude protein contents, phenolic compounds, lipid compositions (fatty acids, phytosterols, and tocopherols), and amino acid compositions of 26 walnut samples from 11 walnut-growing provinces in China. The results indicate that the oil contents of the samples varied from 60.08% to 71.06%, and their protein contents ranged from 7.26 g/100 g to 19.50 g/100 g. The composition of fatty acids corresponded to palmitic acid at 4.61-8.27%, stearic acid at 1.90-3.55%, oleic acid at 15.50-32.28%, linoleic acid at 53.44-67.64%, and α-linolenic acid at 2.45-12.77%. The samples provided micronutrients in widely varying amounts, including tocopherol, phytosterol, and total phenolic content, which were found in the walnut oil samples in amounts ranging from 356.49 to 930.43 mg/kg, from 1248.61 to 2155.24 mg/kg, and from 15.85 to 68.51 mg/kg, respectively. A comprehensive evaluation of walnut oil quality in the samples from the 11 provinces using a principal component analysis was conducted. The findings revealed that the samples from Henan, Gansu, and Zhejiang had the highest composite scores among all provinces. Overall, Yunnan-produced walnuts had high levels of crude fat, polyunsaturated fatty acids, and total tocopherols, making them more suitable for producing high-quality oil, whereas Henan-produced walnuts, although lower in crude fat, had a higher crude protein content and composite score, thus showing the best walnut characteristics.

Screening of Reference miRNA of Different Early- and Late-Flowering Tree Peony Varieties

miRNA plays an important role in plant growth and development and in response to various stresses. Quantitative real-time PCR (qRT-PCR) technology is often used to detect the expression level of miRNAs and genes by comparing with reference genes. In order to screen out the optimal reference miRNAs in different tree peony varieties, the petals of 42 different early- and late-flowering tree peony varieties were used as experimental materials, and geNorm, NormFinder, Bestkeeper, and RefFinder software were used to evaluate the stability of 16 candidate reference miRNAs. The results showed that the average Ct values of all candidate reference miRNAs were between 15.34 ± 0.29 and 32.64 ± 0.38. The optimal number of reference miRNAs was four, which were PsPC-5p-19095, PsPC-3p-51259, PsmiR159a, and PsPC-3p-6660 in geNorm. The stability of PsPC-3p-6660 was the highest in the analysis results of NormFinder software. Among the analysis results of Bestkeeper software, PsMIR319-p5 has the highest stability. Among the results of comprehensive evaluation and analysis of several software using RefFinder, the candidate reference miRNA with the highest stability was PsPC-3p-6660. When PsPC-3p-6660 was used as the reference miRNA, the expression of PomiR171 and PomiR414 in response to different flowering times of tree peony was relatively stable in 42 tree peony varieties, indicating that PsPC-3p-6660 was stable and reliable. The results of this study provide a reference miRNA for studying the expression changes of miRNA in different tree peony varieties and further exploring the regulatory mechanism of miRNA in different peony varieties.

Quality evaluation of oil by cold-pressed peanut from different growing regions in China

In this study, twenty‐six peanut varieties and their cold‐pressed oils from eleven provinces in China were investigated for their oil content, acid value, peroxide value, fatty acid profiles, bioactive constituents, and induction period (IP) of lipid oxidation. Meanwhile, the effect of the geographical origin of peanut on the quality of cold‐pressed peanut oils (CPOs) was studied. The average acid value of CPOs in southern China was higher than that in northern China (0.49 mg KOH/g versus 0.22 mg KOH/g, p > .05). In addition, the average of oleic acid content, ratio of oleic acid to linoleic acid (O/L), and IP were also higher in southern China than that in northern China (p < .05). However, the average content of campesterol, β‐sitosterol, total phytosterol, linoleic acid, and ratio of unsaturated fatty acid to saturated fatty acid (UFA/SFA) exhibited reverse results (p < .05). At last, the comprehensive evaluation of CPOs based on principal component analysis (PCA) was performed. In all samples, Silihong from Liaoning province, northern China was No.1, and Zhonghua 21 from Xiaogan City, Hubei Province was No.4 which was the first one from southern China. Moreover, heat map clustering analysis further revealed the differences and similarities among different samples, and those results were in accordance with the comprehensive evaluation results.

Hetero/Homo-Complexes of Sucrose Transporters May Be a Subtle Mode to Regulate Sucrose Transportation in Grape Berries

The sugar distribution mechanism in fruits has been the focus of research worldwide; however, it remains unclear. In order to elucidate the relevant mechanisms in grape berries, the expression, localization, function, and regulation of three sucrose transporters were studied in three representative Vitis varieties. Both SUC11 and SUC12 expression levels were positively correlated with sugar accumulation in grape berries, whereas SUC27 showed a negative relationship. The alignment analysis and sucrose transport ability of isolated SUCs were determined to reflect coding region variations among V. vinifera, V. amurensis Ruper, and V. riparia, indicating that functional variation existed in one SUT from different varieties. Furthermore, potentially oligomerized abilities of VvSUCs colocalized in the sieve elements of the phloem as plasma membrane proteins were verified. The effects of oligomerization on transport properties were characterized in yeast. VvSUC11 and VvSUC12 are high-affinity/low-capacity types of SUTs that stimulate each other by upregulating V_max and K_m, inhibiting sucrose transport, and downregulating the K_m of VvSUC27. Thus, changes in the distribution of different SUTs in the same cell govern functional regulation. The activation and inhibition of sucrose transport could be achieved in different stages and tissues of grape development to achieve an effective distribution of sugar.

Metabolite Profiles, Bioactivity, and HPLC Fingerprint of Different Varieties of Eucommia ulmoides Oliv.: Towards the Utilization of Medicinal and Commercial Chinese Endemic Tree

Eucommia ulmoides Oliv. is widely regarded in China as a precious medicinal and commercial endemic tree. Due to cross-breeding or natural variation of E. ulmoides, the metabolite composition may vary significantly, making control of the medical quality difficult. In order to improve the rational development and utilization, the quality of seven varieties of E. ulmoides were evaluated based on metabolite profiles (total phenolic, total flavonoid, gutta-percha, aucubin, geniposidic acid, chlorogenic acid, geniposide, pinoresinol diglucoside, rutin, hyperoside, and astragalin), bioactivities (in vitro, in vivo antioxidant activities, and antibacterial activities) and HPLC fingerprint combined with chemometrics analysis. On this basis, the differences of medicinal parts (leaf and bark) were further carried out. For the traditional use of bark, Purple-leaf E. ulmoides was the most suitable. For the use of leaf, Qinzhong 1 and Purple-leaf E. ulmoides were appropriate. HPLC fingerprint analysis showed that significant differences in metabolite profiles exist among seven varieties of E. ulmoides. Combined with chemometrics analysis, seven varieties of E. ulmoides were divided into three groups from the use of leaf and bark. The analysis not only evaluated quality of seven varieties of E. ulmoides, but also could distinguish different varieties and different regions of origin. The results can provide theoretical basis for E. ulmoides resources utilization and cultivation of fine varieties.

Validation of Suitable Reference Genes for Assessing Gene Expression of MicroRNAs in Lonicera japonica

MicroRNAs (miRNAs), which play crucial regulatory roles in plant secondary metabolism and responses to the environment, could be developed as promising biomarkers for different varieties and production areas of herbal medicines. However, limited information is available for miRNAs from Lonicera japonica, which is widely used in East Asian countries owing to various pharmaceutically active secondary metabolites. Selection of suitable reference genes for quantification of target miRNA expression through quantitative real-time (qRT)-PCR is important for elucidating the molecular mechanisms of secondary metabolic regulation in different tissues and varieties of L. japonica. For precise normalization of gene expression data in L. japonica, 16 candidate miRNAs were examined in three tissues, as well as 21 cultivated varieties collected from 16 production areas, using GeNorm, NormFinder, and RefFinder algorithms. Our results revealed combination of u534122 and u3868172 as the best reference genes across all samples. Their specificity was confirmed by detecting the cycling threshold (C t) value ranges in different varieties of L. japonica collected from diverse production areas, suggesting the use of these two reference miRNAs is sufficient for accurate transcript normalization with different tissues, varieties, and production areas. To our knowledge, this is the first report on validation of reference miRNAs in honeysuckle (Lonicera spp.). Restuls from this study can further facilitate discovery of functional regulatory miRNAs in different varieties of L. japonica.