Pathogenesis related-1 proteins in plant defense: regulation and functional diversity.

Climate change-related environmental stresses can negatively impact crop productivity and pose a threat to sustainable agriculture. Plants have a remarkable innate ability to detect a broad array of environmental cues, including stresses that trigger stress-induced regulatory networks and signaling pathways. Transcriptional activation of plant pathogenesis related-1 (PR-1) proteins was first identified as an integral component of systemic acquired resistance in response to stress. Consistent with their central role in immune defense, overexpression of PR-1s in diverse plant species is frequently used as a marker for salicylic acid (SA)-mediated defense responses. Recent advances demonstrated how virulence effectors, SA signaling cascades, and epigenetic modifications modulate PR-1 expression in response to environmental stresses. We and others showed that transcriptional regulatory networks involving PR-1s could be used to improve plant resilience to stress. Together, the results of these studies have re-energized the field and provided long-awaited insights into a possible function of PR-1s under extreme environmental stress.

Establishment of RNAi-Mediated Pest Control Method for Red Imported Fire Ant, Solenopsis invicta.

RNAi plays a crucial role in insect gene function research and pest control field. Nonetheless, the variable efficiency of RNAi across diverse insects and off-target effects also limited its further application. In this study, we cloned six essential housekeeping genes from Solenopsis invicta and conducted RNAi experiments by orally administering dsRNA. Then, we found that mixing with liposomes significantly enhanced the RNAi efficiency by targeting for SiV-ATPaseE. Additionally, we observed a certain lethal effect of this dsRNA on queens by our established RNAi system. Furthermore, no strict sequence-related off-target effects were detected. Finally, the RNAi effect of large-scale bacteria expressing dsRNA was successfully confirmed for controlling S. invicta. In summary, this study established an RNAi system for S. invicta and provided a research template for the future development of nucleic acid drugs based on RNAi.

Insights into Reactive Oxygen Species Production-Scavenging System Involved in Sugarcane Response to Xanthomonas albilineans Infection under Drought Stress.

Plants must adapt to the complex effects of several stressors brought on by global warming, which may result in interaction and superposition effects between diverse stressors. Few reports are available on how drought stress affects Xanthomonas albilineans (Xa) infection in sugarcane (Saccharum spp. hybrids). Drought and leaf scald resistance were identified on 16 sugarcane cultivars using Xa inoculation and soil drought treatments, respectively. Subsequently, four cultivars contrasting to drought and leaf scald resistance were used to explore the mechanisms of drought affecting Xa-sugarcane interaction. Drought stress significantly increased the occurrence of leaf scald and Xa populations in susceptible cultivars but had no obvious effect on resistant cultivars. The ROS bursting and scavenging system was significantly activated in sugarcane in the process of Xa infection, particularly in the resistant cultivars. Compared with Xa infection alone, defense response via the ROS generating and scavenging system was obviously weakened in sugarcane (especially in susceptible cultivars) under Xa infection plus drought stress. Collectively, ROS might play a crucial role involving sugarcane defense against combined effects of Xa infection and drought stress.

Identification of a sugarcane bacilliform virus promoter that is activated by drought stress in plants.

Sugarcane (Saccharum spp.) is an important sugar and biofuel crop in the world. It is frequently subjected to drought stress, thus causing considerable economic losses. Transgenic technology is an effective breeding approach to improve sugarcane tolerance to drought using drought-inducible promoter(s) to activate drought-resistance gene(s). In this study, six different promoters were cloned from sugarcane bacilliform virus (SCBV) genotypes exhibiting high genetic diversity. In ß-glucuronidase (GUS) assays, expression of one of these promoters (PSCBV-YZ2060) is similar to the one driven by the CaMV 35S promoter and >90% higher compared to the other cloned promoters and Ubi1. Three SCBV promoters (PSCBV-YZ2060, PSCBV-TX, and PSCBV-CHN2) function as drought-induced promoters in transgenic Arabidopsis plants. In Arabidopsis, GUS activity driven by promoter PSCBV-YZ2060 is also upregulated by abscisic acid (ABA) and is 2.2-5.5-fold higher when compared to the same activity of two plant native promoters (PScRD29A from sugarcane and PAtRD29A from Arabidopsis). Mutation analysis revealed that a putative promoter region 1 (PPR1) and two ABA response elements (ABREs) are required in promoter PSCBV-YZ2060 to confer drought stress response and ABA induction. Yeast one-hybrid and electrophoretic mobility shift assays uncovered that transcription factors ScbZIP72 from sugarcane and AREB1 from Arabidopsis bind with two ABREs of promoter PSCBV-YZ2060. After ABA treatment or drought stress, the expression levels of endogenous ScbZIP72 and heterologous GUS are significantly increased in PSCBV-YZ2060:GUS transgenic sugarcane plants. Consequently, promoter PSCBV-YZ2060 is a possible alternative promoter for genetic engineering of drought-resistant transgenic crops such as sugarcane.

Biocontrol efficiency and characterization of insecticidal protein from sugarcane endophytic Serratia marcescens (SM) against oriental armyworm Mythimna separata (Walker).

The plant endophytic bacteria are a great source of nature insecticides. However, no such endophytic bacteria have been found in sugarcane, to address this gap, we isolated and identified a strain of Serratia marcescens with moderate insecticidal activity from sugarcane. Taken armyworm Mythimna separata as example, the mortality rates of oral infection and injection infection were 47.06 % and 91 %, respectively. The SM has significant negative affect on the growth, development, and reproduction of M. separata. After determining that these insecticidal substances, 33 potential virulence proteins were screened through the identification and prediction of bacterial proteins. Later we confirmed serralysin was a vital toxic protein from SM that caused M. separata death by prokaryotic expression. In addition, we also found that the intestinal tissue cells infected with SM or serralysin were severely diseased, which may be a major factor in M. separata demise. Finally, through gene expression level, protein molecular docking, we found the aminopeptidase-N would be one of the potential receptors of serralysin. Taken together, our findings indicate that sugarcane endophyte S. marcescens may be beneficial for pest control in sugarcane and explain its insecticidal mechanism. This study provides new ideas and materials for the biological control of pests.

A ScWIP5 gene confers fall armyworm resistance by reducing digestive enzyme activities in sugarcane.

BACKGROUND: The fall armyworm, Spodoptera frugiperda, is one of the most dangerous pests to various crops. As the most crucial sugar crop, sugarcane is also constantly threatened by these pests. Plant wound-induced proteinase inhibitors (WIP) are natural defense proteins that play important roles in the defense system against insect attack. Breeding for resistance would be the best way to improve the variety characteristics and productivity of sugarcane. Screening and verification for potential plant endogenous insect-resistant genes would greatly improve the insect-resistant breeding progress of sugarcane. RESULTS: A sugarcane WIP5 gene (ScWIP5) was up-regulated 536 times after insect feeding treatment on previous published transcriptome databases. ScWIP5 was then cloned and its potential role in sugarcane resistance to fall armyworm evaluated by construction of transgenic Nicotiana benthamiana. The toxicity of ScWIP5 transgenic N. benthamiana to fall armyworm showed lower weight gain and higher mortality compared to wild-type N. benthamiana feeding group. Furthermore, the concentration of JA and NbAOC, NbAOS, and NbLOX from the Jasmin acid biosynthesis pathway was significantly induced in ScWIP5 transgenic N. benthamiana compared to the control. In addition, digestive enzyme actives from the insect gut were also evaluated, and trypsin and cathepsin were significantly lower in insects fed with ScWIP5 transgenic N. benthamiana. CONCLUSION: These results indicate that ScWIP5 might enhance insect resistance by increasing JA signal transduction processes and reducing insect digestive enzyme activities, thus impacting insect growth and development. © 2023 Society of Chemical Industry.

Genome-wide identification of GTE family proteins in sugarcane (Saccharum spontaneum) reveals that SsGTEL3a confers drought tolerance.

The bromodomain is a highly conserved protein domain that specifically binds to acetylated lysine residues in histones, thereby activating transcription of target genes. Although some progress in Global Transcription Factor Group E (GTE) has been achieved in numerous animals and a few plant species, no systematic analysis of GTE gene families has been reported yet in sugarcane. In our study, 37 GTE and GTE-Like (GTEL) genes were characterized in the Saccharum spontaneum. All SsGTE/SsGTEL members were heterogeneously located on all chromosomes of the sugarcane genome and divided into five groups. Transcriptome data showed that SsGTEL3a was expressed at significantly higher levels under drought stress in drought-resistant varieties than in drought-sensitive varieties. Moreover, the overexpression of SsGTEL3a significantly improved the drought tolerance in Arabidopsis through improving the scavenging ability of reactive oxygen species. Additionally, an interaction between ScFAR1 and SsGTEL3a was identified, with ScFAR1 showing a positive response to drought stress in bacterium. In summary, this systematic analysis of GTE gene family in sugarcane and functional research of SsGTEL3a broadened deeper insight into their evolutionary dynamics and functional properties and provided new candidate genes for drought-resistant molecular breeding of sugarcane.

Phylogeny and Genetic Divergence among Sorghum Mosaic Virus Isolates Infecting Sugarcane.

Sorghum mosaic virus (SrMV, the genus Potyvirus of the family Potyviridae) is a causal agent of common mosaic in sugarcane and poses a threat to the global sugar industry. In this study, a total of 901 sugarcane leaf samples with mosaic symptom were collected from eight provinces in China and were detected via RT-PCR using a primer pair specific to the SrMV coat protein (CP). These leaf samples included 839 samples from modern cultivars (Saccharum spp. hybrids) and 62 samples from chewing cane (S. officinarum). Among these, 632 out of 901 (70.1%) samples were tested positive for SrMV. The incidences of SrMV infection were 72.3% and 40.3% in modern cultivars and chewing cane, respectively. Phylogenetic analysis showed that all tested SrMV isolates were clustered into three clades consisting of six phylogenetic groups based on 306 CP sequences (this study = 265 and GenBank database = 41). A total of 10 SrMV isolates from South America (the United States and Argentina) along with 106 isolates from China were clustered in group D, while the remaining 190 SrMV isolates from Asia (China and Vietnam) were dispersed in five groups. The SrMV isolates in group F were limited to Yunnan province in China, and those in group A were spread over eight provinces. A significant genetic heterogeneity was elucidated in the nucleotide sequence identities of all SrMV CPs, ranging from 69.0% to 100%. A potential recombination event was postulated among SrMV isolates based on CP sequences. All tested SrMV CPs underwent dominant negative selection. Geographical isolation (South America vs. Asia) and host types (modern cultivars vs. chewing cane) are important factors promoting the genetic differentiation of SrMV populations. Overall, this study contributes to the global understanding of the genetic evolution of SrMV and provides a valuable resource for the epidemiology and management of the mosaic in sugarcane.

Identification of ARF transcription factor gene family and its defense responses to bacterial infection and salicylic acid treatment in sugarcane.

Auxin response factor (ARF) is a critical regulator in the auxin signaling pathway, involved in a variety of plant biological processes. Here, gene members of 24 SpapARFs and 39 SpnpARFs were identified in two genomes of Saccharum spontaneum clones AP85-441 and Np-X, respectively. Phylogenetic analysis showed that all ARF genes were clustered into four clades, which is identical to those ARF genes in maize (Zea mays) and sorghum (Sorghum bicolor). The gene structure and domain composition of this ARF family are conserved to a large degree across plant species. The SpapARF and SpnpARF genes were unevenly distributed on chromosomes 1-8 and 1-10 in the two genomes of AP85-441 and Np-X, respectively. Segmental duplication events may also contribute to this gene family expansion in S. spontaneum. The post-transcriptional regulation of ARF genes likely involves sugarcane against various stressors through a miRNA-medicated pathway. Expression levels of six representative ShARF genes were analyzed by qRT-PCR assays on two sugarcane cultivars [LCP85-384 (resistant to leaf scald) and ROC20 (susceptible to leaf scald)] triggered by Acidovorax avenae subsp. avenae (Aaa) and Xanthomonas albilineans (Xa) infections and salicylic acid (SA) treatment. ShARF04 functioned as a positive regulator under Xa and Aaa stress, whereas it was a negative regulator under SA treatment. ShARF07/17 genes played positive roles against both pathogenic bacteria and SA stresses. Additionally, ShARF22 was negatively modulated by Xa and Aaa stimuli in both cultivars, particularly LCP85-384. These findings imply that sugarcane ARFs exhibit functional redundancy and divergence against stressful conditions. This work lays the foundation for further research on ARF gene functions in sugarcane against diverse environmental stressors.

The effect of chlorogenic acid, a potential botanical insecticide, on gene transcription and protein expression of carboxylesterases in the armyworm (Mythimna separata).

Chlorogenic acid (CGA) is a potential botanical insecticide metabolite that naturally occurs in various plants. Our previous studies revealed CGA is sufficient to control the armyworm Mythimna separata. In this study, we conducted a proteomic analysis of saliva collected from M. separata following exposure to CGA and found that differentially expressed proteins (DEPs) treated with CGA for 6 h and 24 h were primarily enriched in glutathione metabolism and the pentose phosphate pathway. Notably, we observed six carboxylesterase (CarE) proteins that were enriched at both time points. Additionally, these corresponding genes were expressed at levels 5.05 to 130.25 times higher in our laboratory-selected resistance strains. We also noted a significant increase in the enzyme activity of carboxylesterase following treatments with varying CGA concentrations. Finally, we confirmed that knockdown of MsCarE14, MsCarE28, and MsCCE001h decreased the susceptibility to CGA in resistance strain, indicating three CarE genes play crucial roles in CGA detoxification. This study presents the first report on the salivary proteomics of M. separata, offering valuable insights into the role of salivary proteins. Moreover, the determination of CarE mediated susceptibility change to CGA provides new targets for agricultural pest control and highlights the potential insecticide resistance mechanism for pest resistance management.

Genetic Divergence and Population Structure of Xanthomonas albilineans Strains Infecting Saccharum spp. Hybrid and Saccharum officinarum.

Leaf scald caused by Xanthomonas albilineans (Xa) is a major bacterial disease in sugarcane that represents a threat to the global sugar industry. Little is known about the population structure and genetic evolution of this pathogen. In this study, 39 Xa strains were collected from 6 provinces in China. Of these strains, 15 and 24 were isolated from Saccharum spp. hybrid and S. officinarum plants, respectively. Based on multilocus sequence analysis (MLSA), with five housekeeping genes, these strains were clustered into two distinct phylogenetic groups (I and II). Group I included 26 strains from 2 host plants, Saccharum spp. hybrid and S. officinarum collected from 6 provinces, while Group II consisted of 13 strains from S. officinarum plants in the Zhejiang province. Among the 39 Xa strains, nucleotide sequence identities from 5 housekeeping genes were: ABC (99.6-100%), gyrB (99.3-100%), rpoD (98.4-100%), atpD (97.0-100%), and glnA (97.6-100%). These strains were clustered into six groups (A-F), based on the rep-PCR fingerprinting, using primers for ERIC2, BOX A1R, and (GTG)5. UPGMA and PCoA analyses revealed that group A had the most strains (24), followed by group C with 11 strains, while there was 1 strain each in groups B and D-F. Neutral tests showed that the Xa population in S. officinarum had a trend toward population expansion. Selection pressure analysis showed purification selection on five concatenated housekeeping genes from all tested strains. Significant genetic differentiation and infrequent gene flow were found between two Xa populations hosted in Saccharum spp. hybrids and S. officinarum. Altogether, these results provide evidence of obvious genetic divergence and population structures among Xa strains from China.

WRKY transcription factors in plant defense.

Environmental stressors caused by climate change are fundamental barriers to agricultural sustainability. Enhancing the stress resilience of crops is a key strategy in achieving global food security. Plants perceive adverse environmental conditions and initiate signaling pathways to activate precise responses that contribute to their survival. WRKY transcription factors (TFs) are essential players in several signaling cascades and regulatory networks that have crucial implications for defense responses in plants. This review summarizes advances in research concerning how WRKY TFs mediate various signaling cascades and metabolic adjustments as well as how epigenetic modifications involved in environmental stress responses in plants can modulate WRKYs and/or their downstream genes. Emerging research shows that clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein (Cas)-mediated genome editing of WRKYs could be used to improve crop resilience.

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.

Nano-selenium enhances sugarcane resistance to Xanthomonas albilineans infection and improvement of juice quality.

Selenium is an important trace element that is beneficial to human health and can enhance plant resistance and crop quality. The occurrence of up-to-date nanotechnology greatly promotes the beneficial efficiency of this trace element on crops. The discovery of nano-Se increased the crop quality and reduced plant disease in different plant. In this study, we reduced sugarcane leaf scald disease incidence by exogenously spraying different concentrations (5 mg/L and 10 mg/L) of nano-Se. Additional studies revealed that spraying of nano-Se reduced reactive oxygen species (ROS) and H2O2 accumulation, and increased antioxidant enzyme activities in sugarcane. The nano-selenium treatments also increased the content of jasmonic acid (JA) and the expression of JA pathway genes. Furthermore, we also found that use nano-Se treatment in an appropriate way can enhance the quality of cane juice. The brix of the cane juice of the selenium-enriched treatment was significantly higher than that of the control group, which was 10.98% and 20.81% higher than that of the CK group, respectively. Meanwhile, the content of certain beneficial amino acids was increased, with the highest being 3.9 times higher than the control. Taken together, our findings inferred that nano-Se could act as a potential eco-fungicide to protect sugarcane from can be used as a potential ecological bactericide to protect sugarcane from Xanthomonas albilineans infections, and improve sugarcane quality. The results arising from this study not only introduces an ecological method to control X. albilineans, but also provides a deep insight into this trace elements for improving juice quality.

Genetic and morphological variants of Acidovorax avenae subsp. avenae cause red stripe of sugarcane in China.

Sugarcane (Saccharum spp.) is an important cash crop for production of sugar and bioethanol. Red stripe caused by Acidovorax avenae subsp. avenae (Aaa) is a disease that occurs in numerous sugarcane-growing regions worldwide. In this study, 17 strains of Aaa were isolated from 13 symptomatic leaf samples in China. Nine of these strains produced white-cream colonies on nutrient agar medium while the other eight produced yellow colonies. In pairwise sequence comparisons of the 16S-23S rRNA internally transcribed spacer (ITS), the 17 strains had 98.4-100% nucleotide identity among each other and 98.2-99.5% identity with the reference strain of Aaa (ATCC 19860). Three RFLP patterns based on this ITS sequence were also found among the strains of Aaa obtained in this study. Multilocus sequence typing (MLST) based on five housekeeping genes (ugpB, pilT, lepA, trpB, and gltA) revealed that the strains of Aaa from sugarcane in China and a strain of Aaa (30179) isolated from sorghum in Brazil formed a unique evolutionary subclade. Twenty-four additional strains of Aaa from sugarcane in Argentina and from other crops worldwide were distributed in two other and separate subclades, suggesting that strains of A. avenae from sugarcane are clonal populations with local specificities. Two strains of Aaa from China (CNGX08 forming white-cream colored colonies and CNGD05 forming yellow colonies) induced severe symptoms of red stripe in sugarcane varieties LC07-150 and ZZ8 but differed based on disease incidence in two separate inoculation experiments. Infected plants also exhibited increased salicylic acid (SA) content and transcript expression of gene PR-1, indicating that the SA-mediated signal pathway is involved in the response to infection by Aaa. Consequently, red stripe of sugarcane in China is caused by genetically different strains of Aaa and at least two morphological variants. The impact of these independent variations on epidemics of red stripe remains to be investigated.

Transcriptome analysis of sugarcane reveals rapid defense response of SES208 to Xanthomonas albilineans in early infection.

BACKGROUND: Diseases are the major factor affecting the quality and yield of sugarcane during its growth and development. However, our knowledge about the factors regulating disease responses remain limited. The present study focuses on identifying genes regulating transcriptional mechanisms responsible for resistance to leaf scald caused by Xanthomonas albilineans in S. spontaneum and S. officinarum. RESULTS: After inoculation of the two sugarcane varieties SES208 (S. spontaneum) and LA Purple (S. officinarum) with Xanthomonas albilineans, SES208 exhibited significantly greater resistance to leaf scald caused by X. albilineans than did LA Purple. Using transcriptome analysis, we identified a total of 4323 and 1755 differentially expressed genes (DEGs) in inoculated samples of SES208 and LA Purple, respectively. Significantly, 262 DEGs were specifically identified in SES208 that were enriched for KEGG pathway terms such as plant-pathogen interaction, MAPK signaling pathway, and plant hormone signal transduction. Furthermore, we built a transcriptional regulatory co-expression network that specifically identified 16 and 25 hub genes in SES208 that were enriched for putative functions in plant-pathogen interactions, MAPK signaling, and plant hormone signal transduction. All of these essential genes might be significantly involved in resistance-regulating responses in SES208 after X. albilineans inoculation. In addition, we found allele-specific expression in SES208 that was associated with the resistance phenotype of SES208 when infected by X. albilineans. After infection with X. albilineans, a great number of DEGs associated with the KEGG pathways 'phenylpropanoid biosynthesis' and 'flavonoid biosynthesis' exhibited significant expression changes in SES208 compared to LA Purple that might contribute to superior leaf scald resistance in SES208. CONCLUSIONS: We provided the first systematical transcriptome map that the higher resistance of SES208 is associated with and elicited by the rapid activation of multiple clusters of defense response genes after infection by X. albilineans and not merely due to changes in the expression of genes generically associated with stress resistance. These results will serve as the foundation for further understanding of the molecular mechanisms of resistance against X. albilineans in S. spontaneum.

Synergistic Effects of Organosilicon and Cu(OH)2 in Controlling Sugarcane Leaf Scald Disease.

Sugarcane leaf scald is a systemic disease caused by Xanthomonas albilineans that limits sugarcane yield and quality. Previous research has shown that exogenous application of copper hydroxide to plants is effective in controlling this disease. However, long-term bactericide use causes serious "3R" problems: resistance, resurgence, and residue. It is therefore urgent to discover new methods for the improvement of bactericide efficiency and efficacy. In the present study, disease index values for leaf scald were measured in sugarcane seedlings over time to determine the effects of different concentrations of copper hydroxide, types of silicon additive, and treatment timing after inoculation with X. albilineans on controlling sugarcane leaf scald disease. Our results show copper hydroxide mixed with organosilicon additive could improve the bactericide efficiency and efficacy and reduce the growth of pathogenic bacteria, even at a reduced concentration in both laboratory and field conditions. This study provides an important practical model for controlling sugarcane leaf scald disease by reducing the concentration of bactericide and increasing its efficacy in sugarcane fields.

The insecticidal effect of the botanical insecticide chlorogenic acid on Mythimna separata (Walker) is related to changes in MsCYP450 gene expression.

The oriental armyworm Mythimna separata (Walker) (Lepidoptera: Noctuidae) can feed on the leaves of many crops, resulting in vast areas of damage and severe losses. Therefore, this insect has become a significant agricultural pest in north Asia. In this study, we fed 3rd instar larvae with artificial diets containing different concentrations of chlorogenic acid and found a significant lethal effect and the mortality increased with increasing chlorogenic acid concentration. Next, we measured the sublethal effect of chlorogenic acid at LC20 on the growth and development of M. separata larvae. The durations of the 4th and 5th instar were longer than those of the control group (prolonged by 0.8 and 0.6 days, respectively), and the 6th instar was shorter (by 1.1 days). The total survival rate, pupation rate, eclosion rate, sex ratio, and oviposition amount in the LC20 chlorogenic acid-treated group were significantly lower than those in the control group. Furthermore, transcriptome analysis of 3rd instar larvae fed various concentrations of chlorogenic acid revealed that several MsCYP450 genes were significantly up-regulated, and this finding was further validated by qRT-PCR. In addition, various concentrations of chlorogenic acid and different treatment times significantly affected the enzyme activity of CYP450 in 3rd instar larvae. Importantly, dietary ingestion of dsMsCYP450 significantly reduced the mRNA level of MsCYP450 genes and increased mortality in the presence of chlorogenic acid. Our results revealed that MsCYP6B6, MsCYP321A7, and MsCYP6B7-like play an essential role in the detoxification of chlorogenic acid by M. separata. This study provides evidence of control effect by botanical insecticide chlorogenic acid on M. separata, and potential detoxification mechanism mediated by P450 of botanical insecticide in arthropods.

Systematic and functional analysis of non-specific lipid transfer protein family genes in sugarcane under Xanthomonas albilineans infection and salicylic acid treatment.

Plant non-specific lipid transfer proteins (nsLTPs) are small basic proteins that play a significant regulatory role in a wide range of physiological processes. To date, no genome-wide survey and expression analysis of this gene family in sugarcane has been performed. In this study we identified the nsLTP gene family in Saccharum spontaneum and carried out expression profiling of nsLTPs in two sugarcane cultivars (Saccharum spp.) that have different resistance to leaf scald caused by Xanthomonas albilineans (Xa) infection. The effect of stress related to exogenous salicylic acid (SA) treatment was also examined. At a genome-wide level, S. spontaneum AP85-441 had 71 SsnsLTP genes including 66 alleles. Tandem (9 gene pairs) and segmental (36 gene pairs) duplication events contributed to SsnsLTP gene family expansion. Five SsnsLTP proteins were predicted to interact with five other proteins. Expression of ShnsLTPI.8/10/Gb.1 genes was significantly upregulated in LCP85-384 (resistant cultivar), but downregulated in ROC20 (susceptible cultivar), suggesting that these genes play a positive regulatory role in response of sugarcane to Xa infection. Conversely, ShnsLTPGa.4/Ge.3 appears to act as a negative regulator in response Xa infection. The majority (16/17) of tested genes were positively induced in LCP85-384 72 h after SA treatment. In both cultivars, but particularly in LCP85-384, ShnsLTPIV.3/VIII.1 genes were upregulated at all time-points, suggesting that the two genes might act as positive regulators under SA stress. Meanwhile, both cultivars showed downregulated ShnsLTPGb.1 gene expression, indicating its potential negative role in SA treatment responses. Notably, the ShnsLTPGb.1 gene had contrasting effects, with positive regulation of gene expression in response to Xa infection and negative regulation induced by SA stress. Together, our results provide valuable information for elucidating the function of ShnsLTP family members under two stressors and identified novel gene sources for development of sugarcane that are tolerant of environmental stimuli.

Genome-wide characterization of cys-tathionine-ß-synthase domain-containing proteins in sugarcane reveals their role in defense responses under multiple stressors.

Cys-tathionine-ß-synthase (CBS) domain-containing proteins (CDCPs) are essential for regulating plant responses to various biotic and abiotic stressors. This study describes the systematic identification and characterization of CDCP family genes in Saccharum spontaneum. A total of 95 SsCDCP genes and eight phylogenetic groups were identified that were distributed over 29 chromosomes of the AP85-441 genome. Most (78/95) SsCDCPs underwent fragment duplication events, and 64 gene pairs were located in synteny blocks. Expression profiling of nine ShCDCPs was also carried out in the Saccharum spp. cultivars ROC22 and MT11-611 that are resistant and susceptible to red stripe, respectively, in response to: (i) Infection by the bacterial pathogen Acidovorax avenue subsp. avenae (Aaa); (ii) abiotic stressors (drought and salinity); and (iii) exogenous salicylic acid (SA) treatment. Members of one gene pair (ShCBSD-PB1-5A and ShCBSD-PB1-7A-1) with a fragment duplication event acted as negative regulators in sugarcane under four stresses, as supported by the significantly decreased expression levels of ShCBSD-PB1-5A (23-83%) and ShCBSD-PB1-7A-1 (15-75%) at all-time points, suggesting that they have functional redundancy. Genes in another pair, ShCBS-4C and ShCBS-4D-1, which have a fragment duplication event, play opposing regulatory roles in sugarcane exposed to multiple stresses, particularly Aaa and NaCl treatments. ShCBS-4C expression was significantly decreased by 32-77%, but ShCBS-4D-1 expression was dramatically upregulated by 1.2-6.2-fold in response to Aaa treatment of both cultivars across all-time points. This result suggested that both genes exhibited functional divergence. Meanwhile, the expression of SsCBSDCBS-5A was significantly upregulated in ROC22 by 1.4-4.6-fold in response to the four stressors. These findings provide important clues for further elucidating the function of ShCDCP genes in sugarcane responding to a diverse range of stresses.