Photosynthetic characterization and expression profiles of sugarcane infected by Sugarcane mosaic virus (SCMV).

Sugarcane mosaic virus (SCMV), belonging to genus Potyvirus, family Potyviridae, is a severe pathogen of several agricultural important crops, mainly sugarcane. Due to complex nature of sugarcane, the effect of SCMV pathogenicity on sugarcane photosynthetic systems remains to be explored. In this study, we investigated the alterations occurring in the photosynthetic system in the sugarcane genotypes at the cytopathological, physiological and biological, transcriptome and proteome level. We generated the transcriptome assembly of two genotypes (susceptible Badila and resistant B-48) using Saccharum spontaneum L. as a reference genome. RNA-sequencing data revealed the significant upregulation of NAD(P)H, RubisCO, oxygen-evolving complex, chlorophyll a and b binding protein, Psb protein family, PSI reaction center subunit II, and IVgenes in B-48, as compared to its counterparts. Upregulated genes in B-48 are associated with various processes such as stability and assembly of photosystem, protection against photoinhibition and antiviral defense. The expression pattern of differentially abundant genes were further verified at the proteomics level. Overall, differentially expressed genes/proteins (DEGs/DEPs) showed the consistency of expression at both transcriptome and proteome level in B-48 genotype. Comprehensively, these data supported the efficiency of B-48 genotype under virus infection conditions and provided a better understanding of the expression pattern of photosynthesis-related genes in sugarcane.

Molecular cloning and functional characterization of the promoter of a novel Aspergillus flavus inducible gene (AhOMT1) from peanut.

Peanut is an important oil and food legume crop grown in more than one hundred countries, but the yield and quality are often impaired by different pathogens and diseases, especially aflatoxins jeopardizing human health and causing global concerns. For better management of aflatoxin contamination, we report the cloning and characterization of a novel A. flavus inducible promoter of the O-methyltransferase gene (AhOMT1) from peanut. The AhOMT1 gene was identified as the highest inducible gene by A. flavus infection through genome-wide microarray analysis and verified by qRT-PCR analysis. AhOMT1 gene was studied in detail, and its promoter, fussed with the GUS gene, was introduced into Arabidopsis to generate homozygous transgenic lines. Expression of GUS gene was studied in transgenic plants under the infection of A. flavus. The analysis of AhOMT1 gene characterized by in silico assay, RNAseq, and qRT-PCR revealed minute expression in different organs and tissues with trace or no response to low temperature, drought, hormones, Ca2+, and bacterial stresses, but highly induced by A. flavus infection. It contains four exons encoding 297 aa predicted to transfer the methyl group of S-adenosyl-L-methionine (SAM). The promoter contains different cis-elements responsible for its expression characteristics. Functional characterization of AhOMT1P in transgenic Arabidopsis plants demonstrated highly inducible behavior only under A. flavus infection. The transgenic plants did not show GUS expression in any tissue(s) without inoculation of A. flavus spores. However, GUS activity increased significantly after inoculation of A. flavus and maintained a high level of expression after 48 hours of infection. These results provided a novel way for future management of peanut aflatoxins contamination through driving resistance genes in A. flavus inducible manner.

Differential Protein Expression in Sugarcane during Sugarcane-Sporisorium scitamineum Interaction Revealed by 2-DE and MALDI-TOF-TOF/MS.

To understand the molecular basis of a specific plant-pathogen interaction, it is important to identify plant proteins that respond to the pathogen attack. Two sugarcane varieties, NCo376 and Ya71-374, were used in this study. By applying 2-dimensional electrophoresis (2-DE), the protein expression profile of sugarcane after inoculating with Sporisorium scitamineum was analyzed. In total, 23 differentially expressed proteins were identified by MALDI-TOF-TOF/MS. Bioinformatics analysis revealed that the functions of these 20 differential proteins were associated with such functions as photosynthesis, signal transduction, and disease resistance, while the function of the remaining three proteins was not determined. From above, we can assume that the protein regulatory network during the interaction between sugarcane and S. scitamineum is complicated. This represents the first proteomic investigation focused on highlighting the alterations of the protein expression profile in sugarcane exposed to S. scitamineum, and it provides reference information on sugarcane response to S. scitamineum stress at the protein level.

Field Performance of Transgenic Sugarcane Lines Resistant to Sugarcane Mosaic Virus.

Sugarcane mosaic disease is mainly caused by the sugarcane mosaic virus (SCMV), which can significantly reduce stalk yield and sucrose content of sugarcane in the field. Coat protein mediated protection (CPMP) is an effective strategy to improve virus resistance. A 2-year field study was conducted to compare five independent transgenic sugarcane lines carrying the SCMV-CP gene (i.e., B2, B36, B38, B48, and B51) with the wild-type parental clone Badila (WT). Agronomic performance, resistance to SCMV infection, and transgene stability were evaluated and compared with the wild-type parental clone Badila (WT) at four experimental locations in China across two successive seasons, i.e., plant cane (PC) and 1st ratoon cane (1R). All transgenic lines derived from Badila had significantly greater tons of cane per hectare (TCH) and tons of sucrose per hectare (TSH) as well as lower SCMV disease incidence than those from Badila in the PC and 1R crops. The transgenic line B48 was highly resistant to SCMV with less than 3% incidence of infection. The recovery phenotype of transgenic line B36 was infected soon after virus inoculation, but the subsequent leaves showed no symptoms of infection. Most control plants developed symptoms that persisted and spread throughout the plant with more than 50% incidence. B48 recorded an average of 102.72 t/ha, which was 67.2% more than that for Badila. The expression of the transgene was stable over many generations with vegetative propagation. These results show that SCMV-resistant transgenic lines derived from Badila can provide resistant germplasm for sugarcane breeding and can also be used to study virus resistance mechanisms. This is the first report on the development and field performance of transgenic sugarcane plants that are resistant to SCMV infection in China.