Biology subjects

Tripathy, B. C.

Publications and source records attributed to Tripathy, B. C..

3 recordsLinked to original sources

bioRxiv2024

Overexpression of Sirohydrochlorin Ferrochelatase Boosts Nitrogen Sulfur and Carbon Utilization in Arabidopsis thaliana

Nitrogen deficiency in the soil is a significant agronomic problem, and the application of nitrogenous fertilizers to the soil has environmental concerns, such as sodic soil and the emission of greenhouse gases. To increase the nutrient use efficiency, the cDNA of AtSirB coding for sirohydrochlorin ferrochelatase, responsible for Fe insertion to the tetrapyrrole moiety of sirohydrochlorin, was overexpressed in Arabidopsis thaliana under the control of 35S promoter for increased synthesis of siroheme. The siroheme is a cofactor for the plastidic enzymes nitrite reductase (NiR) and sulfite reductase (SiR), which reduces nitrite and sulfite to ammonium and sulfide, respectively. A three-step process including methylation, oxidation, and ferro-chelation produces siroheme from uroporphyrinogen III, an intermediate of chlorophyll (Chl) biosynthesis. The NiR and SiR gene expression and protein abundance increased in the over-expressers due to the increased AtSirB protein level. It resulted in an increase in N and S assimilation and enhanced protein content of over-expressers. Conversely, the total protein content decreased in antisense plants due to reduced NR and NiR activities. AtSirB over-expressers had higher protein and Chl contents and increased photosynthetic rate and biomass. Under N and S limitation, the protein, Chl, and photosynthetic electron transport rates in AtSirB over-expressers were higher than in WT. Results demonstrate that the SirB that hijacks uroporphyrinogen from the chlorophyll biosynthesis pathway is a crucial player in N and S assimilation. The siroheme is limiting for efficient nitrate and sulfate reduction and utilization. SirB could be genetically manipulated to increase crop productivity for sustainable agriculture.

bioengineering↗

bioRxiv2023

Fortuitous events in the evolution of Light-dependent Protochlorophyllide Oxidoreductase

Light-dependent protochlorophyllide oxidoreductase (LPOR) is a nuclear-encoded photoenzyme in many photosynthetic organisms. LPOR originated in primitive cyanobacterial ancestors during the great oxygenation event that was detrimental to the existence of the oxygen-sensitive LIPOR that prevailed in anoxygenic Earth. Both LIPOR and LPOR catalyse reduction of protochlorophyllide to chlorophyllide in the penultimate step of chlorophyll biosynthesis. Except for angiosperms and gnetophytes several oxygenic phototrophs harbour both LIPOR and LPOR. The coexistence of LIPOR and LPOR in certain phototrophs provides niche spaces for organisms in unconducive environment. The selection pressure of increased O2 concentration, changing light quality and quantity at different depths of the ocean, nutrient status of water, gene reorganization during several endosymbiotic events, horizontal gene transfer, LIPOR gene loss and multiple duplication events played a major role in the evolution and diversification of LPOR and its isoforms in photosynthetic and non-photosynthetic organisms. In the absence of LIPOR angiosperms become vulnerable to protochlorophyllide-sensitized and light-induced oxidative stress mediated by singlet oxygen. To overcome the photo-damage PORA was expressed abundantly in the plastids of etiolated plants. PORB evolved to take over the function of vanishing PORA isoform in light. Brassicales evolved PORC to protect plants from high light and other environmental stresses. HighlightsO_LIProtochlorophyllide oxidoreductase is an important photo-enzyme in angiosperms that needs light as a substrate for the synthesis of chlorophylls. Therefore, angiosperms cannot green in dark although several algae and lower green plants can synthesize chlorophyll in dark due to the presence of light-independent protochlorophyllide oxidoreductase (LIPOR). C_LIO_LIIn response to climate change, during the great oxygenation event light-dependent protochlorophyllide oxidoreductase (LPOR) evolved due to the O2-induced selection pressure that inactivated the oxygen-sensitive LIPOR. C_LIO_LIIncreased O2 concentration, changing light quality and quantity at different depths of ocean, gene reorganization during several endosymbiotic events, selective LIPOR gene loss and multiple duplication events played a major role in the evolution and diversification of LPOR and its isoforms in phototrophs. C_LIO_LIPhylogenetic studies indicate that LPOR genes have been overwhelmingly horizontally transferred between phototrophs and also non phototrophic organisms. C_LIO_LIPresence of LPOR in non-photosynthetic organisms, Mycobacterium and certain fungi suggests that LPOR may have some other reductive functions in these organisms. C_LI

plant biology↗

bioRxiv2021

Coordinated overexpression of OsSUT1, OsSWEET11 and OsSWEET14 in rice impairs carbohydrate metabolism that has implications in plant growth, yield and susceptibility to Xanthomonas oryzae pv oryzae (Xoo)

Enhancing carbohydrate export to sink tissues is considered as a feasible approach for improving photosynthetic efficiency and crop yield. In Oryza sativa Sucrose Transporter OsSUT1 located in companion cells and Sugars Will Eventually be Exported Transporters (SWEETs); OsSWEET11 and OsSWEET14 present in phloem parenchyma mesophyll cell plasma membranes are involved in long distance sucrose transport. OsSWEET11 and OsSWEET14 also play important role in host-pathogen interaction of rice plants and Xanthomonas oryzae pv oryzae (Xoo) that causes bacterial leaf blight. Three genes, OsSUT1, OsSWEET11, and OsSWEET14 were overexpressed under the control of their native promoters in rice to modulate long distance sugar transport and disease resistance. The transgenics displayed several phenotypic aberrations such as reduced plant height and seed weight due to altered sucrose transport and metabolism. Lower sucrose transport rate in transgenics than the WT resulted in reduced sucrose, fructose and glucose and increased starch accumulation in their leaves at the end of dark period. Transcriptional analysis revealed a reduction in the expression of genes involved in sucrose synthesis pathway in transgenics. Normal growth and development of transgenic seedlings were restored in growth media supplemented with 3% sucrose demonstrating in planta sucrose limitation. Remarkably, transgenic lines had diminished susceptibility to Xoo than the WTs due to low sugar content in the leaves demonstrating that rice plants maintain an optimum level of SWEETs for proper plant growth and development, and upregulation of these SWEETs in rice mimicks Xoo attack impelling plants to reduce sugar content in the apoplasm to inhibit pathogen growth.

plant biology↗