Drought resistant microbial preparations are beneficial soil microorganisms that produce plant growth hormone to enhance the drought tolerance of plants and promote plant growth, which is an ideal substitute for traditional chemical drought resistant preparations. In this study, the bacteria obtained in the soils of Wuyishan tea plantation were used as the research object to screen strains with the high secretion indole-3-acetic acid (IAA) ability and strong drought resistance, and the culture conditions optimization and whole genome sequencing analysis were also conducted. A strain SZF7 with high secreting IAA was obtained, which belonged to Bacillus cereus, which had stronger drought resistance than other strains. The optimal culture conditions for IAA secretion of SZF7 were pH 5.0 and 37 ℃ with 24 h incubation, and pH and temperature significantly affected on the IAA secretion. In the COG and KEGG metabolic pathways of SZF7 genome, the genes related to biological metabolism accounted for 47.96% and 68.52% of the total functional genes, respectively. The genes related to plant growth promotion included IAA, siderophore, non-ribosomal peptide synthase (NRPS), lipopeptide compounds and bacillibactin. There were two IAA synthesis pathways in SZF7, one of which was indole-3-pyruvate pathway mediated by indole-3-pyruvate decarboxylase, and the other was tryptamine pathway mediated by indole-3-glycerol phosphate synthase. This study would provide a scientific basis for the application of drought-resistant and growth-promoting bacteria in the production of tea and other cash crops.

To scientifically evaluate the pollination performance of Macadamia integrifolia by the dominant bee species in China (Apis cerana cerana), we investigated the flowering biological characteristics of M. integrifolia, the pollination behavior of A. cerana cerana, and the effects on M. integrifolia yield and quality by A. cerana cerana pollination in Ximeng Va Autonomous county of China. The results showed that the number of flowers per raceme in macadamia cultivars A4 was in a normal distribution, ranging from 174 to 532 flowers, with an average of 334.0±48.8. The most frequent number of flowers range was 272-374, accounting for 72.17%. The order of A4 floret opening was from the base of inflorescence axis to the top, accounting for 60.24%, from the middle of inflorescence axis to both ends, accounting for 34.94%, and from the top to the base of inflorescence axis, accounting for 4.82%. In M. integrifolia full-bloom stage, the number of A. cerana cerana left colony, back to colony, and pollen-collecting workers increased at first, and then decreased with the time. The number of A. cerana cerana left colony, back to colony workers were mainly concentrated in 12: 00—15: 00, and with the peak period at 15: 00, then, it decreased sharply after 16: 00. The number of pollen-collecting back to colony workers was mainly concentrated in 12: 00—14: 00, and with the peak at 13: 00. The number of A. cerana cerana visiting flowers was significantly higher than that of Apis dorsata and Apis florea, but A. cerana cerana had a shorter per raceme visiting time. The number of visiting flowers workers of A. cerana cerana increased at first, then decreased with time, and the time of the visiting activity was mainly concentrated in 13: 00—17: 10. The correlation analysis results showed that the daily collection activities of A. cerana cerana were greatly influenced by light intensity, temperature and humidity. The average fruit setting rate of per raceme of M. integrifolia by A. cerana cerana pollination significantly increased by 64.15%, and the proportion of raceme falling reduced by 55.39% compared with the control, respectively. In addition, the weight, transverse and vertical diameter of single fruit, the seed rate, the kernel rate, total nitrogen content, crude protein content, crude fat content and 22 kinds of fatty acids content of fruit kernels pollinated by A. cerana cerana were higher than those of the control. The content of saturated fatty acids such as octanoic acid, capric acid, behenic acid, and unsaturated fatty acids 11,14-eicosadienoic acid were significantly higher than those of the control (P<0.05). In conclusion, A. cerana cerana pollination could reduce the shedding of inflorescences, significantly increase fruit setting rate, and improve the yield and quality to a certain extent at the M. integrifolia flowering stage.

Salt is a main factor limiting the utilization of saline land in coastal beach. Rice is the preferred food crop for the utilization of salinized land, and some rhizosphere microorganisms can improve the salt resistance of rice. In order to screen suitable rice varieties planted in salinized land, different rice varieties were selected to cultivate under NaCl stress during the whole growth period, and the diversity and structure of bacterial communities in rhizosphere soil were measured and analyzed by Illumina Miseq sequencing technology. The bacterial community diversity in the rhizosphere soil, the species richness of varieties B3 and B6 were significant higher than those of variety B1 in 0.6% NaCl treatments. The community structure, the dominant bacterial phyla were Chloroflexi, Proteobacteria and Actinobacteria with relative abundance more than 10% of three varieties under different concentrations of NaCl treatments. There were differences in the bacterial community structure of rhizosphere soil, and the number and types of enriched species were also different in different rice varieties. Variety B6 enriched fourteen bacterial taxa branches under 0.6% NaCl treatments, such as Acidobacteriae, Nostocaceae Vicinamibacterales, Thermomicrobiales, KD4-96, etc. Therefore, B6 planted in salinized land of coastal mudflat is beneficial to the formation of dominant bacterial community in rhizosphere soil.

The study was aimed to investigate the soil-microbial carbon, nitrogen and phosphorus characteristics of Eucalyptus plantations at different altitude gradients in Hainan Tropical Rainforest National Park. Typical Eucalyptus plantation forests at different altitudes (500 m, 700 m and 900 m) in Wuzhishan were used as the study object, and natural secondary forests at the same altitude were used as the control. Soil organic carbon (SOC) and total nitrogen (TN) content showed a gradual increase with elevation, and total phosphorus (TP) showed a gradual decrease. The range of variation was 13.16-13.58, 0.93-1.15, 0.17-0.19 g/kg, respectively, which was lower than the SOC and TN contents of natural secondary forests, and lower than the national average values of SOC, TN and TP contents of forests. The microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) showed a trend of gradual increase with elevation, and the microbial biomass phosphorus (MBP) content overall showed a decreasing trend with elevation, with the range of 237.46-398.26, 23.04-30.74, 4.77-9.59 mg/kg, respectively, and with the TP contents. TP showed highly significant positive correlation (P<0.01). The differences were not significant compared with those of natural secondary forests at the same elevation. MBC/MBN, MBC/MBP and MBN/MBP all tended to increase with elevation, with ratios ranging from 9.05-13.17, 24.73-80.99 and 2.76-6.60. At 500 m, the MBC/MBP and MBN/MBP of the Eucalyptus plantation were significantly different from those of the natural secondary forest.. The variation of microbial quotient carbon (qMBC), microbial quotient nitrogen (qMBN) and microbial quotient phosphorus (qMBP) at different elevations was 1.89%-3.34%,2.90%-3.23% and 1.33%-5.41%, respectively. qMBC showed a gradual increase in elevation, and qMBP declined with the elevation. qMBC and qMBP were higher than those of natural secondary forests. qMBC and qMBP were higher than those of natural secondary forests. Soil organic carbon and total nitrogen were the key factors affecting the changes. In conclusion, the elevation gradient has a significant impact on the content and stoichiometric ratio of soil-microbial carbon, nitrogen, and phosphorus in Eucalyptus plantations. Compared with natural secondary forests at the same elevation, the soil of Eucalyptus plantations exhibited a deficiency in carbon and phosphorus contents, but enhanced the conversion efficiency of soil carbon and phosphorus to microbial biomass carbon and phosphorus. Based on this, the Eucalyptus plantations in the park should be conserved, and attention should be paid to the influence of carbon and phosphorus elements in the subsequent management.

In order to study the effect of chalcone isomerase on the synthesis of flavonoids during the development of rubber leaves, this study used the CHI functional domain chalcone (PF02431) to identify the HbCHI gene family members of the Ccalcone isomerase, and to analyze the physicochemical properties, conserved domain, conserved motif and phylogenetic tree of the protein sequences. qRT-PCR was used to analyze the expression pattern of HbCHI during the development of rubber leaves. The effect of HbCHI2 on plant flavonoid synthesis was analyzed using Agrobacterium-mediated transient expression technique in Nicotiana benjamina. Nine HbCHI gene family members (HbCHI1-HbCHI9) were identified from the genomic database of H. brasiliensis. The proteins encoded by HbCHI1-HbCHI9 contained 177-474 amino acids with isoelectric points ranging from 5.1 to 9.52. The proteins were mainly hydrophilic proteins. Only HbCHI1 contained 6 conserved motif1-motif6 motifs, and phylogenetic analysis showed that HBCHI1-HBCHI4 was type I CHI. HbCHI6-HbCHI9 showed fatty acid binding sites, which were type III CHI. HbCHI5 was type IV CHI. The relative expression level of HbCHI gene family in rubber trees showed a trend of first decreasing and then increasing from small bronzer to mature stage. The relative expression level was the lowest in light green stage, and the change trend of total flavonoids content was consistent with the relative expression level of CHI gene. Correlation analysis showed that HbCHI2 had the highest significant correlation with flavoniods content. The Pearson coefficient was 0.97. Overexpression of HbCHI2 in N. benjamina promoted the biosynthesis of flavonoids and increased the total flavonoids content in leaves, which was 2.13 times that of control. These results indicate that HbCHI2 gene regulates flavonoid biosynthesis in rubber leaves.

The molecular mechanism underlying white-fleshed pitaya (Hylocereus undatus) in response to MeJA treatment during the fruit postharvest ripening was investigated. The differentially expressed genes (DEGs) response to MeJA treatment were analyzed by the digital gene expression profiling technology. The results showed that compared with the control, a total of 15 596 DEGs, including 6135 up-regulated genes and 9461 down-regulated genes, were identified. Gene ontology analysis showed that most DEGs were involved in cell metabolism, biological regulation, biosynthesis, catalysis, binding activities and transport activities. KEGG pathway enrichment analysis revealed that all DEGs were assigned in many pathways, mainly involving in photosynthesis, plant hormone signal transduction, protein processing and starch and carbohydrate metabolism. Moreover, the transcripts of most genes involved in ethylene-signaling transduction and cell-wall degradation, belonging to ERF, EIN, XTH, PG and XTH family, were found to be significantly down-regulated. These results strongly suggest that MeJA treatment may be involved in delaying the softening of white-pitaya by restraining the ethylene-signaling transduction and retarding the degradation of cell wall during postharvest ripening. The results would lay a foundation for further research on developing the more efficient postharvest preservation technology for tropical fruits.

Dendrobium nobile has a high ornamental value and is one of the important parental plants in the hybridization group of Dendrobium. To explore the physiological and molecular mechanisms of D. nobile flowers in response to high-temperature stress, this study combined water potential, cell membrane permeability monitoring, ethylene-related compound content determination, and transcriptome analysis. Treatment groups were subjected to 36 ℃ high-temperature stress for 5 h, 10 h and 24 h, with a normal temperature culture as the control. The physiological characteristics of D. nobile flowers under 36 ℃ and the transcriptome response to high temperature were studied. The results shoed that 36 ℃ high-temperature stress had almost no effect on the water status and cell membrane permeability of D. nobile flowers within 24h. The content of ethylene precursor (ACC) in the flowers significantly increased in all three high-temperature treatment groups compared to the control (Dno-CK). The number of differentially expressed genes between the 5 h high-temperature treatment and the control group (Dno-CK vs Dno-5h), the 10 h high-temperature treatment and the control (Dno-CK vs Dno-10h), and the 24 h high-temperature treatment and the control (Dno-CK vs Dno-24h) was 25 204, 25 528 and 26 878, respectively, with the number of genes up-and downregulated was approximately 1∶1. As the duration of high-temperature stress increased, the total number of differentially expressed genes in D. nobile flowers gradually rose. KEGG enrichment analysis showed that the differential genes of the three comparison groups were enriched to the monoterpene biosynthesis pathway, indicating that high temperature promoted the synthesis of volatile terpenoids in D. nobile. Functional enrichment analysis indicated that most of the differentially ex-pressed genes in response to high-temperature stress were enriched in pathways related to genetic information processing and metabolic pathways, with the highest number of differential genes in the nucleotide excision repair, starch and sucrose metabolism, and protein processing in the endoplasmic reticulum pathways. This suggests that high temperature stimulates D. nobile flowers to enhance various metabolic activities in response to heat stress. Screening of differentially expressed genes revealed that heat shock protein (HSP) genes in D. nobile flowers were significantly up-regulated in response to high-temperature stress. The HSP genes responding to high-temperature stress within 24 h in D. nobile flowers were primarily the HSP20 genes, followed by the HSP90 genes. Further research on the heat re-sponse genes of D. nobile flowers can focus on the HSP20 and HSP90 genes. This study on the physiological and transcriptome response of D. nobile flowers to high-temperature stress would provide a reference for heat-tolerant breeding research and theoretical support for the cultivation of heat-resistant D. varieties.

Vanda coerulea, an epiphytic plant with bare roots growing in air, has important value for orchid breeding and ornament. Exploring the development and defense mechanism of the aerial roots from the omics level can provide a theoretical basis for comprehensive understanding of the unique adaptation mechanism of aerial roots. In this study, we used three root sites with different developmental levels of V. coerulea aerial roots as materials, combined with transcriptomics and metabolomics, to reveal the development of different parts of V. coerulea roots and the defense mechanisms. Transcription-metabolism analysis showed that the differentially expressed genes (DEGs) and differentially accumulated metabolites (DAMs) were significantly enriched in the metabolic pathway, biosynthesis pathway of various secondary metabolites and pathway of plant hormone signaling in two comparison groups. Transcriptome analysis showed 11 995 DEGs between the meristematic (group A) and elongation (group B) zones of the root, with 6274 up-regulated and 5721 down-regulated. There were 3673 DEGs between the elongation (group B) and maturation zone (group C) of the root, with 1691 up-regulated and 1982 down-regulated. Metabolomic results revealed 102 DAMs between the two comparison groups, with 52 up-regulated and 50 down-regulated. In the development of roots, the relative expression levels of growth regulators such as auxin, gibberellins (GAs) and abscisic acid (ABA) had significant changes in different developmental stages of plant roots. In terms of defense mechanism, the genes related to the synthesis of alkaloids, flavonoids, and lignins were more expressed in the meristem and elongation zone of roots than in the mature zone. The results indicate that aerial roots development under the regulation of the above-mentioned hormones and accumulate a variety of secondary metabolites to improve defensive capabilities.

ELF3 is an important biological clock gene that regulates the input of light signal and the output of circadian rhythm, participating in modulation of many important processes of plants. In order to understand its regulation in the initiation of petal senescence of Oncidium, we conducted cloning and expression analysis of OnELF3 in Oncidium.OnELF3 (GenBank accession number: OL613896) was isolated from the Oncidium petals. OnELF3 had a length of 2208 bp and encoded a protein of 735 amino acids. Subcellular localization showed its expression in the nucleus. Homologous sequence alignment and phylogenetic tree analysis showed that OnELF3 was closest to the counterparts of Dendrobium candidum and Phalaenopsis. Prokaryotic expression analysis showed that the cloned OnELF3 was capable of prokaryotic expression of functional proteins. Its expression patterns under long day, full light, and full darkness conditions were consistent with its function as a circadian clock gene. Real time fluorescence quantitative analysis showed that the expression of OnELF3 was the highest in cracked buds and full-open flowers, indicating that OnELF3 may play a role in both flowering and flower senescence initiation. This study would lay a foundation for further functional identification of OnELF3 in the initiation of flower senescence.

Hongyang kiwifruit is a distinguished variety independently developed in China. It features a distinctive red coloration, possesses high sugar content and low acidity, and is favored for its rich aroma and unique flavor profile. The growth and development of fruits are influenced by a multitude of factors, among which sucrose non-fermentation-1-associated protein kinase 1 (SnRK1) plays a pivotal role in the regulation of carbohydrate metabolism and the response to both biotic and abiotic stresses. Therefore, in this study, we cloned the full-length cDNA of 2 genes in the SnRK1 family of Hongyang kiwifruit, named AcSnRK1.1 and AcSnRK1.2. The physical and chemical properties, gene structure, conserved motifs, protein conserved domains, and cis-acting elements of AcSnRK1.1 and AcSnRK1.2 were systematically analyzed using bioinformatics approaches. The expression characteristics of AcSnRK1.1 and AcSnRK1.2 genes in different tissues and fruits were quantitatively detected by real-time fluorescence. AcSnRK1.1 and AcSnRK1.2 genes contained an open reading frame of 1548 bp and 1545 bp, respectively, encoding proteins containing 515 and 514 amino acids with highly consistent sequences (96.31%) respectively. Both genes contained 10 exons and 2 introns. Bioinformatics analysis showed that AcSnRK1.1 and AcSnRK1.2 had high homology with other plant SnRK1 proteins. The amino acid sequence showed that STKc_AMPK_alpha, AMPK_C and UBA_SnRK1_plant were unique to the SnRK1 family. Evolutionary tree analysis showed that AcSnRK1.1 and AcSnRK1.2 belonged to the SnRK1 family. Tissue specific analysis showed that AcSnRK1.1 and AcSnRK1.2 were expressed in all tissues of Hongyang Kiwifruit, but the expression abundance was the highest in fruit. During fruit development, the expression levels of AcSnRK1.1 and AcSnRK1.2 decreased first and then increased. qRT-PCR analysis showed that the expression of AcSnRK1.1 and AcSnRK1.2 was responsive to ABA, GA₃, ET and CPPU. With the increase of storage time, the expression levels of AcSnRK1.1 and AcSnRK1.2 showed a downward trend first and then an upward trend, suggesting that AcSnRK1 gene might regulate the expression of sucrose synthase. The results of this study indicate that AcSnRK1.1 and AcSnRK1.2 genes play an important role in the development and storage of Hongyang kiwifruit, which would lay a foundation for further elucidation of the functions of AcSnRK1.1 and AcSnRK1.2 genes.