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Abstract Aromatic rice (Oryza sativa) fetches a premium price due to the pleasant aroma. The major aroma compound 2-acetyl-1-pyrroline (2AP) has been found to be enhanced under stress. This condition can be considered to study the genes, precursors, enzymes, and metabolites involved in elevated levels of 2AP biosynthesis. In the present study, 100 mM salt treatment was given to two aromatic rice cultivars Ambemohar-157 (A-157) and Basmati-370 (B-370) at the vegetative stage (VS3). After salt treatment, in the leaves, 2AP contents were elevated by 2.2 and 1.8 fold in A-157 and B-370, respectively. Under these elevated 2AP conditions, the precursor amino acids (glutamate, putrescine, ornithine, and proline), their related genes, enzymes, and metabolites (methylglyoxal and γ-aminobutyric acid (GABA) related to 2AP biosynthesis were analyzed. In addition, agronomic characters were also studied. It was observed that the proline content was enhanced in both the cultivars by 29% (A-157) and 40% (B-370) as compared to control. The Δ1-pyrroline-5-carboxylate synthetase (P5CS) enzyme activity was increased in salt-treated plants leaf tissue by 31% (A-157) and 40% (B-370) compared to control. The P5CS gene expression was enhanced by A-157 (1.8 fold) and B-370 (2.2 fold) compared to control, putrescine content in A-157 and B-370 decreased by 2.5 and 2.7 fold respectively as compared to control. The ornithine decarboxylase (ODC) activity was enhanced in A-157 (12%) and B-370 (35%) over control. Further, ODC gene expression was enhanced in both the cultivars A-157 (1.5 fold) and B-370 (1.3 fold). The diamino oxidase (DAO) enzyme activity was increased by 28% (A-157) and 35% (B-370) respectively over control. The GABA content marginally increased over control in both the cultivars namely, A-157 (1.9%) and B-370 (9.5%). The methylglyoxal levels were enhanced by 1.4 fold in A-157 and 1.6 fold in B-370. Interestingly, the enhancement in 2AP in the vegetative stage also helped to accumulate it in mature grains (twofold in A-157 and 1.5 fold in B-370) without test weight penalty. The study indicated that the ornithine and proline together along with methylglyoxal contribute towards the enhancement of 2AP under salt stress.

Abstract TiO2, ZrO2 and layer-by-layer TiO2–ZrO2 films were prepared by doctor blade method followed by sensitization with natural dye for dye-sensitized solar cell application. The structural and optical, morphological and compositional properties were investigated by X-ray diffraction and UV–Vis spectroscopy, scanning electron microscopy, BET, surface profilometer and energy-dispersive X-ray analyzer, respectively. Dye-sensitized solar cells were fabricated using the prepared electrodes of TiO2, ZrO2 and layer-by-layer TiO2–ZrO2 films sensitized with natural dye extracted from Pandan leaves (Pandanus amaryllifolius). The J–V characteristics were recorded to measure photo-response of fabricated devices and electrochemical impedance spectroscopy to study the electron behavior, series resistance and lifetime. Photovoltaic parameter like short-circuit current, open-circuit voltage, fill factor, and power conversion efficiency were evaluated for fabricated solar cell under artificial light supplied from white LED (15 mW·cm−2). The average values of power conversion efficiency of DSSCs fabricated with TiO2, ZrO2 and layer-by-layer TiO2–ZrO2 photoanodes were found to be 0.65%, 3.04% and 3.13%, respectively.

Over the past decades, numerous efforts were made towards the improvement of cereal crops mostly employing traditional or molecular breeding approaches. The current scenario made it possible to efficiently explore molecular understanding by targeting different genes to achieve desirable plants. To provide guaranteed food security for the rising world population particularly under vulnerable climatic condition, development of high yielding stress tolerant crops is needed. In this regard, technologies upgradation in the field of genome editing looks promising. Clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 is a rapidly growing genome editing technique being effectively applied in different organisms, that includes both model and crop plants. In recent times CRISPR/Cas9 is being considered as a technology which revolutionized fundamental as well as applied research in plant breeding. Genome editing using CRISPR/Cas9 system has been successfully demonstrated in many cereal crops including rice, wheat, maize, and barley. Availability of whole genome sequence information for number of crops along with the advancement in genome-editing techniques provides several possibilities to achieve desirable traits. In this review, the options available for crop improvement by implementing CRISPR/Cas9 based genome-editing techniques with special emphasis on cereal crops have been summarized. Recent advances providing opportunities to simultaneously edit many target genes were also discussed. The review also addressed recent advancements enabling precise base editing and gene expression modifications. In addition, the article also highlighted limitations such as transformation efficiency, specific promoters and most importantly the ethical and regulatory issues related to commercial release of novel crop varieties developed through genome editing.

Fragrance of rice is one of the most valued grain quality character thus, fetches much higher market price. 2-Acetyl-1-Pyrroline (2AP) is major aroma compound found in all parts of plant except root in scented rice. Classical and molecular genetics analyses revealed that a single recessive gene betaine aldehyde dehydrogenase 2 (Osbadh2) is responsible for expression of 2AP in scented rice. Present study was aimed at inducing expression of 2AP in non-scented indica rice cultivar IR-64 by silencing OsBADH2 via RNAi technique. The regeneration protocol for IR 64 was optimised, 2, 4-D (MS + 2 mg/L) for callus induction, BAP (2.5 mg/L) for shoot induction and half MS supplemented with 0.1 mg/L NAA was found optimum for rooting. A vector pBSK was used for construction of RNAi cassette and pRI101-ON as a binary vector. Agrobacterium (GV3101) mediated transformation was done using embryogenic calli of IR-64 and transgenic calli were selected on MS medium containing kanamycin (250 mg/L). Gas chromatography analyses showed significant amount of 2AP (0.05 ppm) production in RNAi callus. The content of precursors, proline and methylglyoxal were not varied but GABA content was found to be reduced in RNAi callus (5.1±0.03 µg/g) than control (6.4±0.05 µg/g). Further transgenic calli showed 7 fold reduction in expression of BADH2 transcript. The transgenic calli have been regenerated and transformed plants are under observation for further transcriptome analysis and 2AP quantification in seeds. The study demonstrated that RNAi approach could be successfully used for imparting pleasant aroma character in non-scented rice cultivars.