Photosynthesis regulation, cell membrane stabilization and methylglyoxal detoxification seems major altered pathways under cold stress as revealed by integrated multi-omics meta-analysis.

Climate change has altered cold weather patterns, resulting in irregular cold weather conditions, and changing the global plant distribution pattern affecting plant development processes resulting in severe yield losses. Although molecular mechanisms and interconnections are quite well studied, a cumulative understanding of plant responses to cold stress (CS) is still lacking. Through meta-analysis, integration of data at the multi-omics level and its correlation with known physiological changes to map and understand the global changes in response to CS was made. Meta-analysis was conducted using the metafor R package program based on physiological parameters like relative electrolytic leakage, malondialdehyde, soluble sugar, proline and antioxidant enzymes activity. Proline and soluble sugars showed the highest (> 1.5 mean fold) change over control thus qualifying as global markers for studying CS. Surprisingly most up-regulated (> 15-fold) DEGs corresponded with the dehydrin family and glyoxalase superfamily proteins. Functional annotations of DEGs corresponded with photosynthesis and glycolysis pathway. Proteins responsible for cell signalling and increased soluble sugars were common in all the datasets studied thus correlating with the transcriptome and proteomic data. Proline and soluble sugars were positively regulated in all the metabolomics datasets. This study supported the earlier known players like proline and soluble sugars. Surprisingly, a new player glyoxalase seems to be contributing in CS. Supplementary Information: The online version contains supplementary material available at 10.1007/s12298-023-01367-9.

Brassica juncea leaf cuticle contains xylose and mannose (xylomannan) which inhibit ice recrystallization on the leaf surface.

MAIN CONCLUSION: Conjugated sugars showed antifreeze activity in the cuticle by ice recrystallization inhibition rather than thermal hysteresis, enhancing freezing capacity at the surface of B. juncea leaves. Antifreeze biomolecules play a crucial role in mitigating the physical damage from frost by controlling extracellular ice crystal growth in plants. Antifreeze proteins (AFPs) are reported from the apoplast of different plants. Interestingly, there is no report about antifreeze properties of the cuticle. Here, we report the potential antifreeze activity in the Brassica juncea (BJ) leaf cuticle. Nano LC-MS/MS analysis of a cuticle protein enriched fraction (CPE) predicted over 30 putative AFPs using CryoProtect server and literature survey. Ice crystal morphology (ICM) and ice recrystallization inhibition (IRI) analysis of ABC supernatant showed heat and pronase-resistant, non-protein antifreeze activities as well as hexagonal ice crystals with TH of 0.17 °C and IRI 46%. The ZipTip processed ABC supernatant (without peptides) had no effect on TH activity, confirming a non-protein antifreeze molecule contributing to activity. To understand the origin and to confirm the source of antifreeze activity, cuticular membranes were isolated by pectinase and cellulase hydrolysis. FTIR analysis of the intact cuticle showed xylose, mannose, cellulose, and glucose. Xylanase and cellulase treatments of the ZipTip processed ABC supernatant led to an increase in sugar content and 50% loss in antifreeze activity. UV spectroscopy and NMR analysis supported the finding of FTIR and enzyme hydrolysis suggesting the contribution of xylose and mannose to antifreeze activity. By TLC analysis, conjugated sugars were found in the cuticle. This work has opened up a new research area where the antifreeze capacity needs to be established with regard to complete characterization and mechanism of action of the antifreeze carbohydrates (conjugated sugars) on the leaf surface.

Effect of Rhizoglomus fasciculatum and Paecilomyces lilacinus in the biocontrol of root-knot nematode, Meloidogyne incognita in Capsicum annuum L.

Root-knot nematodes possess a major threat to agricultural production of various crops worldwide. The intensive use of chemical nematicides to control plant parasitic nematodes has adverse effects on our environment and human health. Owing to the importance of developing new strategies, an experiment was conducted to reveal the influence of arbuscular mycorrhizal fungus, Rhizoglomus fasciculatum and nematophagous fungus, Paecilomyces lilacinus alone or in combination with various organic amendments such as superphosphate, green and organic manure to control the infection of root-knot, nematode Meloidogyne incognita in a vegetable crop Capsicum annuum. These two fungi along with soil amendments significantly improved plant growth and fruit yield and effectively controlled infection of M. incognita. The dual inoculation of P. lilacinus and R. fasciculatum reduced the number of galls and egg masses, thereby revealing the controlled proliferation of M. incognita infection in C. annuum roots. The beneficial effect of these fungi further increased on supplementation of soil with organic or green manures. Inoculation of C. annuum with these two fungi showed a significant increase in egg parasitization; however, maximum effect was detected on dual inoculation. Amongst the soil amendments, the best response was obtained in case of green manure along with mycorrhizal fungus and P. lilacinus. Present study revealed that nematophagous and AM fungi, in combination with green manure were effective in controlling M. incognita, thus suggesting the use of such agents for biocontrol of plant parasitic nematodes in agriculture.