Plant Nitrogen Metabolism: Balancing Resilience to Nutritional Stress andAbiotic Challenges

Plant growth and resilience to abiotic stresses,such as soil salinity and drought,depend intricately on nitrogen metabolism.This review explores nitrogen’s regulatory role in plant responses to these challenges,unveiling a dynamic interplay between nitrogen availability and abiotic stress.In the context of soil salinity,a nuanced rela-tionship emerges,featuring both antagonistic and synergistic interactions between salinity and nitrogen levels.Salinity-induced chlorophyll depletion in plants can be alleviated by optimal nitrogen supplementation;however,excessive nitrogen can exacerbate salinity stress.We delve into the complexities of this interaction and its agri-cultural implications.Nitrogen,a vital element within essential plant structures like chloroplasts,elicits diverse responses based on its availability.This review comprehensively examines manifestations of nitrogen deficiency and toxicity across various crop types,including cereals,vegetables,legumes,and fruits.Furthermore,we explore the broader consequences of nitrogen products,such as N_(2)O,NO_(2),and ammonia,on human health.Understand-ing the intricate relationship between nitrogen and salinity,especially chloride accumulation in nitrate-fed plants and sodium buildup in ammonium-fed plants,is pivotal for optimizing crop nitrogen management.However,prudent nitrogen use is essential,as overapplication can exacerbate nitrogen-related issues.Nitrogen Use Effi-ciency(NUE)is of paramount importance in addressing salinity challenges and enhancing sustainable crop productivity.Achieving this goal requires advancements in crop varieties with efficient nitrogen utilization,pre-cise timing and placement of nitrogen fertilizer application,and thoughtful nitrogen source selection to mitigate losses,particularly urea-based fertilizer volatilization.This review article delves into the multifaceted world of plant nitrogen metabolism and its pivotal role in enabling plant resilience to nutritional stress and abiotic challenges.It offers insights into future directions for sustainable agriculture.

Yellow Vein Mosaic Disease in Okra(Abelmoschus esculentus L.):An Overview on Causal Agent,Vector and Management

Okra(Abelmoschus esculentus L.)belongs to the Malvaceae family and is one of the most essential and popular vegetables globally.It is rich in proteins,carbohydrates,and vitamins.Abiotic and biotic factors threaten okra productivity.Okra yellow vein mosaic disease(OYVMD)is the most destructive disease of okra.The causal agent,[i.e.,Okra yellow vein mosaic virus(OYVMV)]of this disease belongs to the family Geminiviridae and genus Begomovirus.OYVMV is a monopartite with additional ssDNA molecule.This virus has two components DNA-A for protein coding and DNA-B for symptoms induction.Whitefly transmits OYVMV in persistent manner.Characteristic symptoms of OYVMV infected okra plants are chlorosis,dwarfing,and yellowing of veins and fruits.High temperatures with moderate rainfall enhance the development of OYVMV disease and the whitefly population.However,high humidity with low temperature and rainfall has no significant role in developing the OYVMD and whitefly population.Moreover,the virus also affects the secondary metabolites in the infected okra plants.The virus can be managed through various strategies including the application of plant defense activators,the development of resistant varieties and by controlling its vector via pesticides and plant extracts.Various plant defense activators such as monopotassium phosphate(KH2PO),salicylic acid,benzoic acid,and citric acid enhance resistance in okra against OYMVD.In addition,the resistance to OYMVD can also be achieved by successfully incorporating high yielding but resistant cultivars of acceptable quality.In this review,we have discussed history,economic impact,symptomology,disease development under a natural environment,genetics and management of OYVMV.

Fusarivirus accessory helicases present an evolutionary link for viruses infecting plants and fungi

A significant number of mycoviruses have been identified that are related to plant viruses,but their evolutionary relationships are largely unexplored.A fusarivirus,Rhizoctonia solani fusarivirus 4(RsFV4),was identified in phytopathogenic fungus Rhizoctonia solani(R.solani)strain XY74 co-infected by an alphaendornavirus.RsFV4 had a genome of 10,833 nt(excluding the poly-A tail),and consisted of four non-overlapping open reading frames(ORFs).ORF1 encodes an 825 aa protein containing a conserved helicase domain(Hel1).ORF3 encodes 1550 aa protein with two conserved domains,namely an RNA-dependent RNA polymerase(RdRp)and another helicase(Hel2).The ORF2 and ORF4 likely encode two hypothetical proteins(520 and 542 aa)with unknown functions.The phylogenetic analysis based on Hel2 and RdRp suggest that RsFV4 was positioned within the fusarivirus group,but formed an independent branch with three previously reported fusariviruses of R.solani.Notably,the Hel1 and its relatives were phylogenetically closer to helicases of potyviruses and hypoviruses than fusariviruses,suggesting fusarivirus Hel1 formed an evolutionary link between these three virus groups.This finding provides evidence of the occurrence of a horizontal gene transfer or recombination event between mycoviruses and plant viruses or between mycoviruses.Our findings are likely to enhance the understanding of virus evolution and diversity.