The Responses of Sucrose Metabolism and Carbon Translocation in Tomato Seedlings under Different Light Spectra.

Light plays a dominant role in the biosynthesis and accumulation of photosynthetic products. However, the metabolism and translocation of photosynthetic products in plants under different light spectra remain elusive. In this study, tomato (Solanum lycopersicum L.) seedlings were treated with different light spectra delivered by light-emitting diodes (LEDs) with the same photosynthetic photon flux density at 300 µmol m-2 s-1, including monochromatic red (660 nm, R), blue (450 nm, B), sun-like white (W, 380-780 nm), or a combination of R and B lights (R:B = 1:1, RB). Compared with W, the biomass distribution ratio for leaves under R, B, and RB decreased by 5.01-9.53%, while the ratio for stems and roots increased by 3.71-6.92% and 0.14-2.81%, respectively. The photosynthetic carbon distribution expressed as 13C enrichment was higher in stems and roots under RB and R, while B led to more 13C transported from leaves and enriched in stems when compared with W. Meanwhile, RB led to significant increases in the activities of phosphate synthase (SPS), sucrose synthase (SS), vacuolar acid invertase (VI), and neutral invertase (NI). The R was more efficient in increasing the activity of SPS and SS, while B was more effective in promoting the activity of VI and NI. The transcript levels of SPS, SS3, NI6, and VI were upregulated under R, B, and RB. However, the transcript patterns of SPS, SS3, NI6, and VI were not consistent with the changes in their encoded enzymes, especially the transcript patterns of SPS and SS3. Our study suggests that the red- and blue-light-induced long-distance and short-distance transport of photosynthetic products in plants, respectively, might result from different regulation of sucrose-metabolizing enzymes from transcriptional and post-transcriptional levels.

Metabolic Resistance of Sogatella furcifera (Hemiptera: Delphacidae) toward Pymetrozine Involves the Overexpression of CYP6FJ3.

Sogatella furcifera (Horváth), which mainly threatens rice, shows various levels of pesticide resistance due to long-term overuse of pesticides. Our resistance monitoring of 20 field populations in Sichuan, China, revealed that they were susceptible to highly resistant toward pymetrozine (0.4-142.2 RR), and JL21 reached the highest level of resistance. The JL21 population exhibited cross-resistance to triflumezopyrim and dinotefuran but sensitivity to sulfoxaflor, acetamiprid, clothianidin, and nitenpyram. The increased P450 activity were support to involve in pymetrozine resistance by detoxification enzyme activities and synergist determination. Among 16 candidate P450 genes, CYP6FJ3 (5.25-fold) was the most up-regulated in JL21, while no significant change was found after LC25 pymetrozine treatment. Furthermore, the knockdown by RNAi and heterologous overexpression by the GAL4/UAS system confirmed that the CYP6FJ3 overexpression was involved in the pymetrozine resistance, and recombination in vitro confirmed that CYP6FJ3 could hydroxylate pymetrozine. Therefore, the overexpression of CYP6FJ3 promotes pymetrozine metabolic resistance in S. furcifera.

Eco-friendly deacetylated chitosan base siRNA biological-nanopesticide loading cyromazine for efficiently controlling Spodoptera frugiperda.

Spodoptera frugiperda is a serious threat to various crops, such as corn and rice, and results in severe economic losses. Herein, a chitin synthase sfCHS highly expressed in the epidermis of S. frugiperda was screened, and when interfered by an sfCHS-siRNA nanocomplex, most individuals could not ecdysis (mortality rate 53.3 %) or pupate (abnormal pupation 80.6 %). Based on the results of structure-based virtual screening, cyromazine (CYR, binding free energy -57.285 kcal/mol) could inhibit ecdysis (LC50, 19.599 µg/g). CYR-CS/siRNA nanoparticles encapsulating CYR and SfCHS-siRNA with chitosan (CS) were successfully prepared, as confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and 74.9 mg/g CYR was characterized in the core of CYR-CS/siRNA by high-performance liquid chromatography and Fourier transform infrared spectroscopy. Small amounts of prepared CYR-CS/siRNA containing only 1.5 µg/g CYR could better inhibit chitin synthesis in the cuticle and peritrophic membrane (mortality rate 84.4 %). Therefore, chitosan/siRNA nanoparticle-loaded pesticides were useful for pesticide reduction and comprehensive control of S. frugiperda.

Status of Fungicide Resistance and Physiological Characterization of Tebuconazole Resistance in Rhizocotonia solani in Sichuan Province, China.

The resistance prevalence of chemical fungicides has caused increasingly serious agro-ecological environmental problems. However, there are few previous reports about resistance to succinate dehydrogenase (SDHI) or sterol demethylation inhibitor (DMI) in Rhizoctonia solani, one of the main agro-diseases. In this study, the fungicide resistance of 122 R. solani isolates in Sichuan Province was monitored by the mycelial growth rate method. Results showed that all isolates were susceptible to hexaconazole and most isolates were susceptible to thifluzamide, except for the field isolate MSRS-2-7 due to a moderate resistance to thifluzamide (16.43-fold resistance ratio, RR), compared to the sensitivity baseline of thifluzamide (0.042 µg/mL EC50 values). On the contrary, many isolates showed moderate or high resistance to tebuconazole (10.59- to 60.78-fold RR), reaching EC50 values of 0.54~3.10 µg/mL, especially for a highly resistant isolate LZHJ-1-8 displaying moderate resistance to epoxiconazole (35.40-fold RR due to a 3.54 µg/mL EC50 value). The fitness determination found that the tebuconazole-resistant isolates showed higher fitness cost with these characteristics, including a lower growth rate, higher relative electric conductivity, an increased ability to tolerate tebuconazole, and high osmotic pressure. Four new mutations of cytochrome P450 sterol 14α-demethylase (CYP51), namely, S94A, N406S, H793R, and L750P, which is the target for DMI fungicides, was found in the tebuconazole-resistant isolates. Furthermore, the lowest binding energy with tebuconazole was also found in the LZHJ-1-8 isolate possessing all the mutations through analyses with Discovery Studio software. Therefore, these new mutation sites of CYP51 may be linked to the resistance against tebuconazole, and its application for controlling R. solani should be restricted in some areas.

Resistance of Sogatella furcifera to triflumezopyrim mediated with the overexpression of CYPSF01 which was regulated by nuclear receptor USP.

Sogatella furcifera is one of the main agricultural pests in many Asian countries, bringing about enormous injury. A triflumezopyrim-resistant (Tri) strain of S. furcifera was established through continuous screening in laboratory. The determination of synergist and enzyme activity indicated that P450s, especially for the upregulation expression of CYPSF01, played a key role in the increased resistance, confirmed by RNAi, and the recombinant protein of CYPSF01 and NADPH-P450 reductase was able to degrade triflumezopyrim. CYPSF01 had an obviously co-expression relationship with nuclear receptor ultraspiracle (USP), which were all significantly up-regulated when exposed to triflumezopyrim. Further, a USP-binding motif MA0534.1 was enriched from the upregulated peaks by Assay for Transposase Accessible Chromatin (ATAC-seq) analysis, which exited in the peaks located on the promoter of CYPSF01; the yeast one-hybrid experiments confirmed that USP could bind to the CYPSF01 promoter. And the USP interference significantly down-regulated CYPSF01 expression, and resulted in the significantly increasing sensitivity to triflumezopyrim, its mortality rate increased 28.37%. Therefore, the overexpression of USP could cause to the overexpression of CYPSF01, ultimately resulting in the resistance to triflumezopyrim in S. furcifera.

Maf regulates the overexpression of CYP307A1, which is involved in the fitness advantage of bistrifluron-resistant Spodoptera litura (Fab.) (Noctuidae: Lepidoptera).

Spodoptera litura is a widely distributed multifeeding pest, that has developed high resistance to many chemical insecticides. In the present study, a bistrifluron-resistant (Bis-SEL) strain showing 113.8-fold resistance ratio relative to a bistrifluron-susceptible (Bis-UNSEL) strain was obtained and showed a fitness advantage (resurgence). First, we found that the observed resurgence might have resulted from Maf transcription factor overexpression in the Bis-SEL strain, which would influence the synthesis of ecdysone and chitin. Additionally, a co-expression relationship between Maf and CYP307A1 was verified by weighted correlation network analysis (WGCNA) and qRT-PCR, and the expression of CYP307A1, a key gene in ecdysone synthesis, was significantly downregulated by Maf interference. The assay for transposase-accessible chromatin with high-throughput sequencing (ATAC-seq) and a yeast one-hybrid showed that Maf could bind to the cncc:maf-s element in the CYP307A1 promoter region. The synthesis of ecdysone, which stimulated chitin synthesis, was also decreased significantly following Maf and CYP307A1 interference. Therefore, the upregulation of Maf expression leaded to the upregulation CYP307A1 expression, which led to an increase in the synthesis of ecdysone, resulting in resurgence accompanied by resistance to bistrifluron.

The fitness advantages of bistrifluron resistance related to chitin synthase A in Spodoptera litura (Fab.) (Noctuidae: Lepidoptera).

BACKGROUND: Spodoptera litura is one of the major agricultural pests in China, and it has developed serious resistance to many traditional chemical insecticides. In the present study, the bistrifluron-resistant (Bis-SEL) strain accompanied by a higher oviposition, 113.8-fold RR compared to the bistrifluron-susceptible (Bis-UNSEL) strain, was obtained by bidirectional screening. A comparison of their gonad coefficiency and genes related to oviposition or resistance was used to elucidate the resurgence mechanism. RESULTS: The ovarian index, oviposition, and potential egg production in the Bis-SEL strain of female adults were significantly higher than those in the Bis-UNSEL strain, and the length of ovariole in the Bis-SEL strain was also significantly elongated. The protein contents of vitellogenin (Vg) and vitellogenin receptor (VgR) in the Bis-UNSEL strain were lower than those in the Bis-SEL strain, consistent with their gene expressions levels, and there was a significantly positive linear correlation between Vg and VgR protein contents, further confirming that resistant strains have high reproductive fitness. Moreover, the chitin synthase A in the Bis-SEL strain was clearly up-regulated, and a mutation (H866Y) near the QRRRW in the catalytic domain caused a rise in the hydrogen bond between UDP-GlcNAc and chitin synthase, and its chitin content was higher than that in the Bis-UNSEL strain. Nevertheless, the sensitivity of the Bis-SEL strain to bistrifluron was significantly recovered when it was knocked down though RNA interference. CONCLUSION: The fitness advantages of bistrifluron resistance may be related to the up-regulation and mution of chitin synthase A. © 2021 Society of Chemical Industry.