Browsing by Author "Saini, Deepak"

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Differential regulation of nitric oxide mediated by phytoglobin1 plays a role in resistance during Botrytis cinerea infection in Arabidopsis thaliana
(Springer Nature Publishing AG, 2026) Jaiswal, Rekha; Saini, Deepak; Swain, Jagannath; Gupta, Kapuganti Jagadis
Botrytis cinerea is a prominent necrotrophic pathogen responsible for gray mold disease, affecting a wide range of plant species, including economically vital crops such as tomatoes, grapes, strawberries, etc. Nitric oxide (NO) is considered as a crucial player in plant responses to biotic stress. NO homeostasis is regulated by phytoglobin (Pgb1), a potential scavenger of NO. However, the role of the Pgb1-NO cycle in regulating defense response against B. cinerea remains largely unknown. In the current study, we investigated the defense response of Arabidopsis thaliana against B. cinerea infection using antisense (Pgb1 AS) and overexpression (Pgb1 OE) lines, which produce differential levels of NO. The Pgb1 AS line accumulated higher NO levels and conferred resistance against B. cinerea infection, with reduced ROS levels, reduced cell death, and increased stomatal closure. Conversely, Pgb1 OE showed reduced NO levels accompanied by increased susceptibility. The elevated NO level in Pgb1 AS was associated with increased nitrate reductase (NR) activity and upregulation of NIA1 and NIA2 gene expression. Interestingly, ethylene-mediated defense pathway genes such as ERF1, ACS2, and ACS6 were upregulated while pathogen-related genes such as PR1, PR2, PR5, and NPR1 were downregulated in Pgb1 AS line. The elevated expression of ethylene genes corresponded with the higher ethylene levels in Pgb1 AS. Overall, our results confirmed the crucial role of phytoglobin-modulated NO in defense against B. cinerea infection by activating the ethylene-mediated defense pathway.
Expression analysis of ROS-related genes during the germination of chickpea (Cicer Arietinum L.) seeds
(Springer Nature Publishing AG, 2026) Babuta, Priyanka; Samant, Sanjib Bal; Saini, Deepak; Gupta, Kapuganti Jagadis
Seed germination is a critical physiological process that transforms a quiescent seed into a metabolically active seedling and is also a crucial factor in determining maximum crop production. This transition is influenced by various intrinsic and extrinsic factors. Interestingly, reactive oxygen species (ROS) plays an important role in breaking seed dormancy by oxidation of biomolecules, weakening of the testa and degradation of endosperm. Similarly, molecular internal oxygen is also considered vital for the transition of dormancy to seed germination. However, it is essential to establish a correlation between the internal oxygen and the generation of ROS during seed germination. This chapter details protocols for imaging internal oxygen concentrations using VisiSens and fluorescent detection of ROS using H2DCFDA in chickpea seeds, complemented by qPCR analysis of key ROS-related genes (RBOH, AOX 1, UCP 1, and NADH dehydrogenase). These findings from these methods help advance our understanding of the inverse relationship between molecular oxygen and ROS dynamics during seed germination.
Moderate modulation by S-nitrosoglutathione of photorespiratory enzymes in pea (Pisum sativum) leaves, compared to the strong effects of high light
(Springer Nature Publishing AG, 2024) Saini, Deepak; Bapatla, Ramesh B.; Vemula, Chandra Kaladhar; Gahir, Shashibhushan; Bharath, Pulimamidi; Gupta, Kapuganti Jagadis; Raghavendra, Agepati S.
When plants are exposed to water stress, photosynthesis is downregulated due to enhanced reactive oxygen species (ROS) and nitric oxide (NO). In contrast, photorespiratory metabolism protected photosynthesis and sustained yield. Modulation of photorespiration by ROS was established, but the effect of NO on photorespiratory metabolism was unclear. We, therefore, examined the impact of externally added NO by using S-nitrosoglutathione (GSNO), a natural NO donor, in leaf discs of pea (Pisum sativum) under dark or light: moderate or high light (HL). Maximum NO accumulation with GSNO was under high light. The presence of 2-4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO), a NO scavenger, prevented the increase in NO, confirming the release of NO in leaves. The increase in S-nitrosothiols and tyrosine-nitrated proteins on exposure to GSNO confirmed the nitrosative stress in leaves. However, the changes by GSNO in the activities and transcripts of five photorespiratory enzymes: glycolate oxidase, hydroxypyruvate reductase, catalase, glycerate kinase, and phosphoglycolate phosphatase activities were marginal. The changes in photorespiratory enzymes caused by GSNO were much less than those with HL. Since GSNO caused only mild oxidative stress, we felt that the key modulator of photorespiration might be ROS, but not NO.
Nitric oxide-mediated modulation of photorespiratory enzymes and photochemical components in leaves of pea plants (Pisum sativum)
(John Wiley & Sons, 2026) Saini, Deepak; Bharath, Pulimamidi; Gahir, Shashibhushan; Pandey, Jayendra; Vemula, Chandra Kaladhar; Gupta, Kapuganti Jagadis; Subramanyam, Rajagopal; Raghavendra, Agepati S
The photorespiratory metabolism safeguards photosynthesis against abiotic and biotic stress. Nitric oxide (NO) and reactive oxygen species (ROS) levels rise in plants during abiotic stress. Low concentrations of NO or ROS are beneficial as signalling molecules, but they can be toxic to plant cells at high concentrations. ROS are known to modulate photorespiration; however, it is unclear whether NO affects photorespiratory enzymes and photochemical components simultaneously. We therefore used sodium nitroprusside (SNP) under dark, moderate light (ML), or high light (HL) conditions to simultaneously investigate its impact on photorespiratory enzymes and photochemical components. The NO levels were increased upon SNP exposure in Pisum sativum leaves, particularly under HL conditions. The NO release in leaves was confirmed when the NO scavenger cPTIO (2-(4-Carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide potassium salt) was present, since it decreased the majority of elevated NO. The nitrosative/oxidative stress in Pisum sativum leaves was confirmed by the increase in nitrosothiols and tyrosine-nitrated proteins, as well as reduced aconitase activity after SNP exposure at HL. The protein levels, mRNA levels, and the enzyme activities of the following four photorespiratory enzymes: glycolate oxidase (GO), hydroxypyruvate reductase (HPR), glycerate kinase (GK), and phosphoglycolate phosphatase (PGLP) were markedly increased under elevated NO conditions. Catalase (CAT), ascorbate peroxidase (APX), and superoxide dismutase (SOD) also showed increased activity, elevated protein and transcript levels upon exposure to SNP. Parallel studies on chlorophyll a fluorescence confirmed that NO restricted electron transport at both PSII and PSI, inhibited photosynthesis and respiration, and damaged photosynthetic pigments. We concluded from this study that NO at high concentrations upregulated photorespiratory enzymes while inhibiting photochemical components such as photosystem II and I (PSII/PSI) simultaneously.