The manuscript highlights the role of antioxidants in alleviation of salinity stress in two principal legume crops Cyamopsis tetragonoloba and Vigna radiata of Indian Thar Desert. The study evaluates correlation between the antioxidants of two cultivars in terms of morphological and physiological alterations. Hydroponically acclimatized seedlings of both the crops were subjected to NaCl stress at different concentrations ranges from 10 to 100 mM. After 96 h, the treated legumes were harvested to analyze the cellular homeostasis and salt tolerance mechanism via examining growth, stress parameters, osmoprotectants and enzymatic antioxidants. Differential response in the antioxidants activity was observed in crops. Equal contribution of antioxidants in mitigation of salinity stress was recorded in C. tetragonoloba while V. radiata shows greater tolerance by accumulating greater amount of proline which is approximately 2.72 folds higher than C. tetragonoloba. Moreover, the NR and HO1 activities in V. radiata were recorded to be 2.76 and 1.55 folds respectively which is 1.2 times higher in comparison to C. tetragonoloba. The detrimental effect of NaCl in terms of MDA content was also higher in V. radiata which concluded that V. radiata is more reactive towards salinity stress than C. tetragonoloba. The study is significant as this is the first report illustrating the sensitivity and tolerance level of NaCl in legumes of Thar Desert.
Bilins are open‐chain tetrapyrroles with a wide range of visible and nearly visible‐light absorption and emission properties. The linear tetrapyrrole molecules function as chromophores of the light‐harvesting phycobiliproteins and phytochrome‐mediated light sensing in photosynthetic organisms. They are derived from the cyclic precursor haem. The initial step in bilin biosynthesis is the conversion of haem into biliverdin (BV IX α) catalysed by haem oxygenase, which is subsequently reduced to specific bilins by ferredoxin‐dependent bilin reductases (FDBRs). Bilins usually bound to apoproteins via single or double covalent bonds to form a macromolecular complex phycobilisomes. The attachment of apoproteins to bilin is an autocatalytic process, but bilin lyases are required for the specific attachment of bilin chromophores to phycobiliprotein apoproteins. Besides the biosynthesis, structure and functions of bilins, this article also aims to recapitulate and discuss the current progress in the field of bilins and to emphasise the emerging areas.
Key Concepts
Bilins are open‐chain tetrapyrrole non‐metallic colour compounds formed as a metabolic product of protoporphyrin IX.
Biliverdin IX α is the common precursor of all naturally occurring bilins.
Haem oxygenase (HO) and ferredoxin‐dependent bilin reductases (FDBRs) are the two key enzymes involved in the biosynthesis of bilins.
Phycobiliproteins assemble with bilins to form phycobilisomes, which help in light harvesting and energy transfer.
Bilin plays a significant role in various physiological processes, namely, photosynthesis, respiration, light perception, signalling, cell defence against oxidative stress, nitrate and sulfate assimilation and programmed cell death.
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