In silico identification of papaya genome-encoded microRNAs to target begomovirus genes in papaya leaf curl disease.

Papaya leaf curl disease (PaLCuD) is widespread and classified in the genus begomovirus (Geminiviridae), disseminated by the vector whitefly Bemisia tabaci. RNA interference (RNAi)-based antiviral innate immunity stands as a pivotal defense mechanism and biological process in limiting viral genomes to manage plant diseases. The current study aims to identify and analyze Carica Papaya locus-derived capa-microRNAs with predicted potential for targeting divergent begomovirus species-encoded mRNAs using a 'four integrative in silico algorithms' approach. This research aims to experimentally activate the RNAi catalytic pathway using in silico-predicted endogenous capa-miRNAs and create papaya varieties capable of assessing potential resistance against begomovirus species and monitoring antiviral capabilities. This study identified 48 predicted papaya locus-derived candidates from 23 miRNA families, which were further investigated for targeting begomovirus genes. Premised all the four algorithms combined, capa-miR5021 was the most anticipated miRNA followed by capa-miR482, capa-miR5658, capa-miR530b, capa-miR3441.2, and capa-miR414 'effective' papaya locus-derived candidate capa-miRNA and respected putative binding sites for targets at the consensus nucleotide position. It was predicted to bind and target mostly to AC1 gene of the complementary strand and the AV1 gene of the virion strand of different begomovirus isolates, which were associated with replication-associated protein and encapsidation, respectively, during PaLCuD. These miRNAs were also found targeting betaC1 gene of betasatellite which were associated with retardation in leaf growth and developmental abnormalities with severe symptoms during begomovirus infection. To validate target prediction accuracy, we created an integrated Circos plot for comprehensive visualization of host-virus interaction. In silico-predicted papaya genome-wide miRNA-mediated begomovirus target gene regulatory network corroborated interactions that permit in vivo analysis, which could provide biological material and valuable evidence, leading to the development of begomovirus-resistant papaya plants. The integrative nature of our research positions it at the forefront of efforts to ensure the sustainable cultivation of papaya, particularly in the face of evolving pathogenic threats. As we move forward, the knowledge gained from this study provides a solid foundation for continued exploration and innovation in the field of papaya virology, and to the best of our knowledge, this study represents a groundbreaking endeavor, undertaken for the first time in the context of PaLCuD research.

Plant Adaptation and Tolerance to Heat Stress: Advance Approaches and Future Aspects.

Heat stress impacts plant growth at all phases of development, although the particular threshold for heat tolerance varies significantly across different developmental stages. During seed germination, elevated temperatures can either impede or completely halt the process, contingent upon the plant type and the severity of the stress. During advanced stages, high temperatures can have a negative impact on photosynthesis, respiration, water balance, and membrane integrity. Additionally, they can also influence the levels of hormones and primary and secondary metabolites. In addition, during the growth and development of plants, there is an increased expression of various heat shock proteins, as well as other proteins related to stress, and the generation of reactive oxygen species (ROS). These are significant plant responses to heat stress. Plants employ several strategies to deal with heat stress, such as maintaining the stability of their cell membranes, removing harmful reactive oxygen species (ROS), producing antioxidants, accumulating and adjusting compatible solutes, activating mitogen-activated protein kinase (MAPK) and calcium-dependent protein kinase (CDPK) cascades, and, crucially, signaling through chaperones and activating transcription. These molecular-level systems boost the ability of plants to flourish in heat stress. Potential genetic methods to enhance plant heat stress resistance encompass old and modern molecular breeding techniques and transgenic approaches, all of which rely on a comprehensive comprehension of these systems. Although several plants exhibit enhanced heat tolerance through traditional breeding methods, the effectiveness of genetic transformation techniques has been somewhat restricted. The latter results from the current constraints in our understanding and access to genes that have known impacts on plant heat stress tolerance. However, these challenges may be overcome in the future. Besides genetic methods, crops' heat tolerance can be improved through the pre-treatment of plants with various environmental challenges or the external application of osmoprotectants such as glycine betaine and proline. Thermotolerance is achieved through an active process in which plants allocate significant energy to maintain their structure and function to avoid damage induced by heat stress. The practice of nanoparticles has been shown to upgrade both the standard and the quantity of produce when crops are under heat stress. This review provides information on the effects of heat stress on plants and explores the importance of nanoparticles, transgenics, and genomic techniques in reducing the negative consequences of heat stress. Furthermore, it explores how plants might adapt to heat stress by modifying their biochemical, physiological, and molecular reactions.

An Insight into Emerging Begomoviruses and their Satellite Complex causing Papaya Leaf Curl Disease.

Papaya leaf curl disease (PaLCD) was primarily detected in India and causes major economic damage to agriculture crops grown globally, seriously threatening food security. Begomoviruses are communicated by the vector Bemisia tabaci, and their transmission efficiency and persistence in the vector are the highest, exhibiting the widest host range due to adaptation and evolution. Symptoms induced during PaLCD include leaf curl, leaf yellowing, interveinal chlorosis, and reduced fruit quality and yield. Consequently, plants have evolved several multi-layered defense mechanisms to resist Begomovirus infection and distribution. Subsequently, Begomovirus genomes organise circular ssDNA of size ~2.5-2.7 kb of overlapping viral transcripts and carry six-seven ORFs encoding multifunctional proteins, which are precisely evolved by the viruses to maintain the genome-constraint and develop complex but integrated interactions with a variety of host components to expand and facilitate successful infection cycles, i.e., suppression of host defense strategies. Geographical distribution is continuing to increase due to the advent and evolution of new Begomoviruses, and sweep to new regions is a future scenario. This review summarizes the current information on the biological functions of papaya-infecting Begomoviruses and their encoded proteins in transmission through vectors and modulating host-mediated responses, which may improve our understanding of how to challenge these significant plant viruses by revealing new information on the development of antiviral approaches against Begomoviruses associated with PaLCD.

Evolutionary Dynamics of Begomoviruses and Its Satellites Infecting Papaya in India.

The genus Begomovirus represents a group of multipartite viruses that significantly damage many agricultural crops, including papaya, and influence overall production. Papaya leaf curl disease (PaLCD) caused by the complex begomovirus species has several important implications and substantial losses in papaya production in many developing countries, including India. The increase in the number of begomovirus species poses a continuous threat to the overall production of papaya. Here, we attempted to map the genomic variation, mutation, evolution rate, and recombination to know the disease complexity and successful adaptation of PaLCD in India. For this, we retrieved 44 DNA-A and 26 betasatellite sequences from GenBank reported from India. An uneven distribution of evolutionary divergence has been observed using the maximum-likelihood algorithm across the branch length. Although there were phylogenetic differences, we found high rates of nucleotide substitution mutation in both viral and sub-viral genome datasets. We demonstrated frequent recombination of begomovirus species, with a maximum in intra-species recombinants. Furthermore, our results showed a high degree of genetic variability, demographic selection, and mean substitution rate acting on the population, supporting the emergence of a diverse and purifying selection of viruses and associated betasatellites. Moreover, variation in the genetic composition of all begomovirus datasets revealed a predominance of nucleotide diversity principally driven by mutation, which might further accelerate the advent of new strains and species and their adaption to various hosts with unique pathogenicity. Therefore, the finding of genetic variation and selection emphases on factors that contribute to the universal spread and evolution of Begomovirus and this unanticipated diversity may also provide guidelines toward future evolutionary trend analyses and the development of wide-ranging disease control strategies for begomoviruses associated with PaLCD.

Role of Diversity and Recombination in the Emergence of Chilli Leaf Curl Virus.

Chilli leaf curl virus (ChiLCV), (Genus Begomovirus, family Geminiviridae) and associated satellites pose a serious threat to chilli production, worldwide. This study highlights the factors accountable for genetic diversity, recombination, and evolution of ChiLCV, and associated chilli leaf curl alphasatellite (ChiLCA) and chilli leaf curl betasatellite (ChiLCB). Phylogenetic analysis of complete genome (DNA-A) sequences of 132 ChiLCV isolates from five countries downloaded from NCBI database clustered into three major clades and showed high population diversity. The dN/dS ratio and Tajima D value of all viral DNA-A and associated betasatellite showed selective control on evolutionary relationships. Negative values of neutrality tests indicated purified selection and an excess of low-frequency polymorphism. Nucleotide diversity (π) for C4 and Rep genes was higher than other genes of ChiLCV with an average value of π = 18.37 × 10-2 and π = 17.52 × 10-2 respectively. A high number of mutations were detected in TrAP and Rep genes, while ChiLCB has a greater number of mutations than ChiLCA. In addition, significant recombination breakpoints were detected in all regions of ChiLCV genome, ChiLCB and, ChiLCA. Our findings indicate that ChiLCV has the potential for rapid evolution and adaptation to a range of geographic conditions and could be adopted to infect a wide range of crops, including diverse chilli cultivars.

Chilli leaf curl disease populations in India are highly recombinant, and rapidly segregated.

Capsicum annuum, a valuable spice and vegetable crop belonging to the Solanaceae family, is extensively grown across the Indian subcontinent. Chilli production is restricted by a begomoviral infection named as chilli leaf curl disease (ChiLCD) mainly in tropical and subtropical regions which leads to considerable economic losses, thus affecting chilli cultivation. Here, we studied the genetic diversity with structural evaluation of chilli leaf curl disease and satellite molecules infecting Chilli in India. We retrieved 121 reference sequences of ChiLCD including DNA-A, DNA-B, beta-satellite and alpha-satellites from GenBank reported from India. The population diversity and genetic variation were estimated through various parameters which decipher the four major groups of phylogenetic divergence for DNA-A and five groups of beta-satellite showing percentage similarity with isolates within and across India. Further, transitional and transversional bias for ORFs were observed highest in C4 and REn genes, respectively, and for DNA-A and DNA-B, these values were 1.07 and 1.22, respectively. The recombination breakpoints for DNA-A were estimated 49 majorly in V1, C1,C2 and C4 genome region and highest 22 breakpoints were determined for Rep (AC1) of ORFs, similarly 9 events for beta-satellite were found less around ßC1ORF. Moreover, the evolution and genetic variability were also contributed through parameters such as nucleotide substitution which were found within the range of RNA viruses for DNA-A, DNA-B, for all 6 ORFs (relaxed clock) and beta-satellite. Additionally, total numbers of mutations (η) for DNA-A, DNA-B, alpha-satellites and beta-satellites were 2505, 419, 807 and 1288 detected, respectively, while it was found 987 highest for Rep gene among all ORFs. Further, neutrality tests determine the dominant nature of population expansion and purifying selection for all the genes of begomovirus associated with ChiLCD and satellite molecules supporting conserved nature of gene. The combined Tajima's D and Fu and Li'S D* negative values in tests indicated that population are under purified selection and an excess of low-frequency polymorphism. Our analysis indicates the potential contribution of genetic mutations and recombination of ChiLCD which leads to rapid adaptation and evolution of begomovirus and its satellite molecules accelerating its host range and diversity within and across the Indian subcontinent. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13205-022-03139-w.

Metal absorption properties of Mentha spicata grown under tannery sludge amended soil-its effect on antioxidant system and oil quality.

Tannery sludge (TS) is hazardous to environment and its disposal in an ecofriendly manner is a major challenge. An experiment was conducted to investigate the metal absorption properties of Mentha spicata grown under different levels of TS amended soil (soil: sludge in 100:0, 75:25, 50:50, 25:75 and 0:100 ratio) and its effect on the antioxidant system and oil quality. At 75:25 ratio of sludge and soil, metal translocation factor was ≥0.5 for Cr, Cd, and Co and for Ni and for Pb ≥ 1. Carvone, limonene, dihydrocarvone and other oil constituents along with biomass were maximum in 75:25 ratio of sludge and soil. Superoxide dismutase (SOD), CAT (Catalases), POD (Peroxidases), MDA (Malondialdehyde) and proline play a major role in detoxification of reactive oxygen species generated due to TS (heavy metal stress). Antioxidant (SOD, CAT and POD), MDA and proline showed an increasing trend as the concentration of TS increased with the treatments. To test the relationship between 23 character principal component analysis (PCA) was performed. PC-I contributed 56% of total variance while PC-II contributed 37% of total variance. The results concluded that M. spicata performed well in terms of oil yield and multiple metal translocations in 75:25 sludge and soil ratio.