Adsorption-desorption behavior of florpyrauxifen-benzyl on three microplastics in aqueous environment as well as its mechanism and various influencing factors.

Microplastics (MPs) and pesticides are two categories contaminants with proposed negative impacts to aqueous ecosystems, and adsorption of pesticides on MPs may result in their long-range transport and compound combination effects. Florpyrauxifen-benzyl, a novel pyridine-2-carboxylate auxin herbicide has been widely used to control weeds in paddy field, but the insights of which are extremely limited. Therefore, adsorption and desorption behaviors of florpyrauxifen-benzyl on polyvinyl chloride (PVC), polyethylene (PE) and disposable face masks (DFMs) in five water environment were investigated. The impacts of various environmental factors on adsorption capacity were evaluated, as well as adsorption mechanisms. The results revealed significant variations in adsorption capacity of florpyrauxifen-benzyl on three MPs, with approximately order of DFMs > PE > PVC. The discrepancy can be attributed to differences in structural and physicochemical properties, as evidenced by various characterization analysis. The kinetics and isotherm of florpyrauxifen-benzyl on three MPs were suitable for different models, wherein physical force predominantly governed adsorption process. Thermodynamic analysis revealed that both high and low temperatures weakened PE and DFMs adsorption, whereas temperature exhibited negligible impact on PVC adsorption. The adsorption capacity was significantly influenced by most environmental factors, particularly pH, cations and coexisting herbicide. This study provides valuable insights into the fate of florpyrauxifen-benzyl in presence of MPs, suggesting that PVC, PE and DFMs can serve as carriers of florpyrauxifen-benzyl in aquatic environment.

Genome-wide association study of kernel colour traits and mining of elite alleles from the major loci in maize.

BACKGROUND: Maize kernel colour is an important index for evaluating maize quality and value and mainly entails two natural pigments, carotenoids and anthocyanins. To analyse the genetic mechanism of maize kernel colour and mine single nucleotide polymorphisms (SNPs) related to kernel colour traits, an association panel including 244 superior maize inbred lines was used to measure and analyse the six traits related to kernel colour in two environments and was then combined with the about 3 million SNPs covering the whole maize genome in this study. Two models (Q + K, PCA + K) were used for genome-wide association analysis (GWAS) of kernel colour traits. RESULTS: We identified 1029QTLs, and two SNPs contained in those QTLs were located in coding regions of Y1 and R1 respectively, two known genes that regulate kernel colour. Fourteen QTLs which contain 19 SNPs were within 200 kb interval of the genes involved in the regulation of kernel colour. 13 high-confidence SNPs repeatedly detected for specific traits, and AA genotypes of rs1_40605594 and rs5_2392770 were the most popular alleles appeared in inbred lines with higher levels. By searching the confident interval of the 13 high-confidence SNPs, a total of 95 candidate genes were identified. CONCLUSIONS: The genetic loci and candidate genes of maize kernel colour provided in this study will be useful for uncovering the genetic mechanism of maize kernel colour, gene cloning in the future. Furthermore, the identified elite alleles can be used to molecular marker-assisted selection of kernel colour traits.

Influence of Planting Density on Sweet Potato Storage Root Formation by Regulating Carbohydrate and Lignin Metabolism.

An appropriate planting density could realize the maximum yield potential of crops, but the mechanism of sweet potato storage root formation in response to planting density is still rarely investigated. Four planting densities, namely D15, D20, D25, and D30, were set for 2-year and two-site field experiments to investigate the carbohydrate and lignin metabolism in potential storage roots and its relationship with the storage root number, yield, and commercial characteristics at the harvest period. The results showed that an appropriate planting density (D20 treatment) stimulated cambium cell differentiation, which increased carbohydrate accumulation and inhibited lignin biosynthesis in potential storage roots. At canopy closure, the D20 treatment produced more storage roots, particularly developing ones. It increased the yield by 10.18-19.73% compared with the control D25 treatment and improved the commercial features by decreasing the storage root length/diameter ratio and increasing the storage root weight uniformity. This study provides a theoretical basis for the high-value production of sweet potato.

Degradation of a New Herbicide Florpyrauxifen-Benzyl in Water: Kinetics, Various Influencing Factors and Its Reaction Mechanisms.

Florpyrauxifen-benzyl is a novel herbicide used to control weeds in paddy fields. To clarify and evaluate its hydrolytic behavior and safety in water environments, its hydrolytic characteristics were investigated under varying temperatures, pH values, initial mass concentrations and water types, as well as the effects of 40 environmental factors such as microplastics (MPs) and disposable face masks (DFMs). Meanwhile, hydrolytic products were identified by UPLC-QTOF-MS/MS, and its hydrolytic pathways were proposed. The effects of MPs and DFMs on hydrolytic products and pathways were also investigated. The results showed that hydrolysis of florpyrauxifen-benzyl was a spontaneous process driven by endothermic, base catalysis and activation entropy increase and conformed to the first-order kinetics. The temperature had an obvious effect on hydrolysis rate under alkaline condition, the hydrolysis reaction conformed to Arrhenius formula, and activation enthalpy, activation entropy, and Gibbs free energy were negatively correlated with temperature. Most of environmental factors promoted hydrolysis of florpyrauxifen-benzyl, especially the cetyltrimethyl ammonium bromide (CTAB). The hydrolysis mechanism was ester hydrolysis reaction with a main product of florpyrauxifen. The MPs and DFMs did not affect the hydrolytic mechanisms but the hydrolysis rate. The results are crucial for illustrating and assessing the environmental fate and risks of florpyrauxifen-benzyl.

The Regulatory Network of Sweet Corn (Zea mays L.) Seedlings under Heat Stress Revealed by Transcriptome and Metabolome Analysis.

Heat stress is an increasingly significant abiotic stress factor affecting crop yield and quality. This study aims to uncover the regulatory mechanism of sweet corn response to heat stress by integrating transcriptome and metabolome analyses of seedlings exposed to normal (25 °C) or high temperature (42 °C). The transcriptome results revealed numerous pathways affected by heat stress, especially those related to phenylpropanoid processes and photosynthesis, with 102 and 107 differentially expressed genes (DEGs) identified, respectively, and mostly down-regulated in expression. The metabolome results showed that 12 or 24 h of heat stress significantly affected the abundance of metabolites, with 61 metabolites detected after 12 h and 111 after 24 h, of which 42 metabolites were detected at both time points, including various alkaloids and flavonoids. Scopoletin-7-o-glucoside (scopolin), 3-indolepropionic acid, acetryptine, 5,7-dihydroxy-3',4',5'-trimethoxyflavone, and 5,6,7,4'-tetramethoxyflavanone expression levels were mostly up-regulated. A regulatory network was built by analyzing the correlations between gene modules and metabolites, and four hub genes in sweet corn seedlings under heat stress were identified: RNA-dependent RNA polymerase 2 (RDR2), UDP-glucosyltransferase 73C5 (UGT73C5), LOC103633555, and CTC-interacting domain 7 (CID7). These results provide a foundation for improving sweet corn development through biological intervention or genome-level modulation.

First report of Capsicum chlorosis virus naturally infecting Ageratum conyzoides in China.

Capsicum chlorosis virus (CaCV; family Tospoviridae, genus Orthotospovirus) was first reported to infect capsicum (Capsicum annuum) and tomato (Solanum lycopersicum) in Australia in 2002 (McMichael et al., 2002). Subsequently, its infection was detected in different plants including waxflower (Hoya calycina Schlecter) in the United States (Melzer et al. 2014), peanut (Arachis hypogaea) in India (Vijayalakshmi et al. 2016), and spider lily (Hymenocallis americana) (Huang et al. 2017), Chilli pepper (Capsicum annuum) (Zheng et al. 2020), and Feiji cao (Chromolaena odorata) (Chen et al. 2022) in China. Ageratum conyzoides L. (commonly known as goat weed, family Asteraceae) is a natural weed in crop fields distributed in subtropical and tropical areas and a reservoir host of numerous plant pathogens (She et al. 2013). In April 2022, we observed that 90% of plants of A. conyzoides in maize fields in Sanya, Hainan province, China, exhibited typical virus-like symptoms of vein yellowing, leaf chlorosis, and distortion (Fig. S1 A-C). Total RNA was extracted from one symptomatic leaf of A. conyzoides. Small RNA libraries were constructed using the small RNA Sample Pre Kit (Illumina, San Diego, USA) for sequencing with an Illumina Novaseq 6000 platform (Biomarker Technologies Corporation, Beijing, China). A total 15,848,189 clean reads were obtained after removing low-quality reads. Quality-controlled qualified reads were assembled into contigs using Velvet 1.0.5 software with a k-mer value of 17. One hundred contigs shared nucleotide identity ranging from 85.7% to 100% with the CaCV using BLASTn searches online (https://blast.ncbi.nlm.nih.gov/Blast.cgi?). Numerous contigs (45, 34, and 21) obtained in this study were mapped to the L, M, and S RNA segments of the CaCV-Hainan isolate (GenBank accession no. KX078565- KX078567) from spider lily (Hymenocallis americana) in Hainan province, China, respectively. The full-length of L, M, and S RNA segments of CaCV-AC were determined to be 8,913, 4,841, and 3,629 bp, respectively (GenBank accession no. OQ597167- OQ597169). Furthermore, five symptomatic leaf samples were tested to be positive for CaCV using a CaCV enzyme-linked immunosorbent assay (ELISA) kit (MEIMIAN, Jiangsu, China) (Fig. S1-D). Total RNA from these leaves was amplified by RT-PCR with two sets of primer pairs. Primers CaCV-F (5'-ACTTTCCATCAACCTCTGT-3') and CaCV-R (5'-GTTATGGCCATATTTCCCT-3') were used for the amplification of 828 bp fragment from nucleocapsid protein (NP) on CaCV S RNA. While another, primers gL3637 (5'-CCTTTAACAGTDGAAACAT-3') and gL4435c (5'-CATDGCRCAAGARTGRTARACAGA-3') were used for the amplification of 816 bp fragment from RNA-dependent RNA polymerase (RdRP) on CaCV L RNA (Fig. S1-E and -F) (Basavaraj et al. 2020). These amplicons were cloned into the pCE2 TA/Blunt-Zero vector (Vazyme, Nanjing, China) and three independent positive colonies of Escherichia coli DH5α carrying each viral amplicon were sequenced. These sequences were deposited in the GenBank database under accession nos. OP616700-OP616709. Pairwise sequence comparison revealed that nucleotide sequences of NP and RdRP genes of the five CaCV isolates shared 99.5% (812 bp out of 828 bp) and 99.4% (799 bp out of 816 bp) nucleotide identities, respectively. They showed 86.2-99.2% and 86.5-99.1% nucleotide identities with corresponding nucleotide sequences of other CaCV isolates derived from GenBank database, respectively. The highest nucleotide sequence identity (99%) of the CaCV isolates obtained in the study was observed with the CaCV-Hainan isolate. Phylogenetic analysis based on NP amino acid demonstrated that six CaCV isolates (this study = 5 and NCBI database = 1) clustered into one distinct clade (Fig. S2). Our data confirmed for the first time the presence of CaCV naturally infecting A. conyzoides plant in China, which enriches information on the host range and will be helpful for disease management.

Divergent adaptations of leaf functional traits to light intensity across common urban plant species in Lanzhou, northwestern China.

Leaves are the most important photosynthetic organs in plants. Understanding the growth strategy of leaves in different habitats is crucial for elucidating the mechanisms underlying plant response and adaptation to the environment change. This study investigated the scaling relationships of the laminar area (LA), leaf fresh mass (LFM), leaf dry mass (LDM), and explored leaf nitrogen (N) and phosphorus (P) content in leaves, and the relative benefits of these pairwise traits in three common urban plants (Yulania denudata, Parthenocissus quinquefolia, and Wisteria sinensis) under different light conditions, including (full-sun and canopy-shade). The results showed that: the scaling exponent of LDM vs LA (> 1, p < 0.05) meant that the LDM increased faster than LA, and supported the hypothesis of diminishing returns. The LFM and LDM had isometric relationships in all the three species, suggesting that the leaf water content of the leaves was nearly unaltered during laminar growth. Y. denudata and W. sinensis had higher relative benefit in full-sun habitats, while the reverse was observed in P. quinquefolia. The N and P content and the N:P ratio in full-sun leaves were generally higher than those of canopy-shade leaves. The leaves of the three urban plants exhibited a shift in strategy during transfer from the canopy shaded to the sunny habitat for adapting to the lower light conditions. The response of plant leaves to the environment shapes the rich variations at the leaf level, and quantification of the relative benefits of plants in different habitats provides novel insights into the response and adaptation strategies of plants.

First Report of Puccinia engleriana Causing Leaf Rust of Tabernaemontana bufalina in Hainan, China.

Tabernaemontana bufalina Lour. is extensively cultivated as an ornamental plant in Hainan, Guangdong, and other regions of southern China. In January 2020, we observed a rust disease on T. bufalina leaves in Sanya (18.15。N and 109.30。E) Hainan, China, and the rust occurred all year-round. In the early stage of rust, yellow chlorotic spots appeared, and then uredinia on the abaxial leaf surface became visible. Uredinia (approximately 200-700 µm in diameter) were mostly yellowish-brown in color, solitary, and irregularly scattered. In the late stage of the disease, spots were connected into lesions, and eventually, the whole leaf became severely chlorotic. Urediniospores were light brown, subglobose, measured 25-30 µm × 20-25 µm. They had two pores and were echinulate with spines spaced 2-5 µm. The teliospores were naked, scattered, or aggregated on severely infected leaves. They were two-celled, measured 33-40 µm × 25-30 µm, elliptic, dark brown, and covered with tiny spines. The teliospores had a colorless pedicel at one end which was approximately 28-34 µm long and enlarged at the lower part. The morphological characteristics of the spores were consistent with the descriptions of Puccinia engleriana Henn. (Hennings 1905). In China, P. engleriana was first identified on the leaves of Tabernaemontana divaricata (L.) in Yunnan province, and recorded as new to China in 2012 (Zhuang 2012). Untill now, no leaf rust caused by P. engleriana has been reported in Hainan. Urediniospores were collected and DNA was extracted using a Quick-DNA extraction Kit (TIANGEN Biotech, Beijing, China). The nuclear large subunit (28S) region of the ribosomal DNA repeat was amplified with primers Rust28SF (Aime et al. 2018) and LR5 (Vilgalys and Hester 1990) following the protocol of Aime and McTaggart (2021). The length of the large subunit sequence was 1,010 bp. When searched the GenBank database, the sequence showed 97.07% homology to the large subunit ribosomal RNA gene (Sequence ID: MW147048.1) of P. engleriana, and 92.5% similarity with 18S ribosomal RNA gene (Sequence ID: KM249855.1) of P. hemerocallidis. This result was consistent with the morphological identification. As for the 3% difference in large subunit ribosomal RNA gene, it was speculated that it may be related to the differences of geographical distribution and host plants, as the reference P. engleriana was obtained from Tabernaemontana orientalis in Australia (Aime and McTaggart 2021). The large subunit sequence was submitted into the GenBank database, with accession No. MZ314895. T. bufalina cutting seedlings with 4 available leaves were used in the Koch's postulate test. These seedlings were planted in a greenhouse with a 14 h/10 h light/dark photoperiod at 28°C and 65% humidity. The urediniospores suspension (5107/ml in 0.05% Tween 20 solution) was sprayed on 6 healthy seedlings and other 6 seedlings were sprayed with 0.05% Tween 20 solution as a negative control. Two weeks after inoculation, leaf chlorosis and yellowish uredinia were observed on the inoculated seedlings, whereas the non-inoculated seedlings stayed healthy. To our knowledge, this is the first report of P. engleriana causing leaf rust on T. bufalina in Hainan province. This report will provide the reference for future investigation of T. bufalina leaf rust, and for further improvement on the knowledge of the geographical distribution of P. engleriana in China.

Salt Stress Modulates the Landscape of Transcriptome and Alternative Splicing in Date Palm (Phoenix dactylifera L.).

Date palm regards as a valuable genomic resource for exploring the tolerance genes due to its ability to survive under the sever condition. Although a large number of differentiated genes were identified in date palm responding to salt stress, the genome-wide study of alternative splicing (AS) landscape under salt stress conditions remains unknown. In the current study, we identified the stress-related genes through transcriptomic analysis to characterize their function under salt. A total of 17,169 genes were differentially expressed under salt stress conditions. Gene expression analysis confirmed that the salt overly sensitive (SOS) pathway genes, such as PdSOS2;1, PdSOS2;2, PdSOS4, PdSOS5, and PdCIPK11 were involved in the regulation of salt response in date palm, which is consistent with the physiological analysis that high salinity affected the Na+/K+ homeostasis and amino acid profile of date palm resulted in the inhibition of plant growth. Interestingly, the pathway of "spliceosome" was enriched in the category of upregulation, indicating their potential role of AS in date palm response to salt stress. Expectedly, many differentially alternative splicing (DAS) events were found under salt stress conditions, and some splicing factors, such as PdRS40, PdRSZ21, PdSR45a, and PdU2Af genes were abnormally spliced under salt, suggesting that AS-related proteins might participated in regulating the salt stress pathway. Moreover, the number of differentially DAS-specific genes was gradually decreased, while the number of differentially expressed gene (DEG)-specific genes was increased with prolonged salt stress treatment, suggesting that AS and gene expression could be distinctively regulated in response to salt stress. Therefore, our study highlighted the pivotal role of AS in the regulation of salt stress and provided novel insights for enhancing the resistance to salt in date palm.