Strigolactones (SLs), being a new class of plant hormones, play regulatory roles against abiotic stresses in plants. There are multiple hormonal response pathways, which are adapted by the plants to overcome these stressful environmental constraints to reduce the negative impact on overall crop plant productivity. Genetic modulation of the SLs could also be applied as a potential approach in this regard. However, endogenous plant hormones play central roles in adaptation to changing environmental conditions, by mediating growth, development, nutrient allocation, and source/sink transitions. In addition, the hormonal interactions can fine-tune the plant response and determine plant architecture in response to environmental stimuli such as nutrient deprivation and canopy shade. Considerable advancements and new insights into SLs biosynthesis, signaling and transport has been unleashed since the initial discovery. In this review we present basic overview of SL biosynthesis and perception with a detailed discussion on our present understanding of SLs and their critical role to tolerate environmental constraints. The SLs and abscisic acid interplay during the abiotic stresses is particularly highlighted.Main Conclusion: More than shoot branching Strigolactones have uttermost capacity to harmonize stress resilience.

The biological activity of natural and novel strigolactone D-lactam analogues is assessed using a novel bioassay based on Arabidopsis transgenic lines expressing AtD14 fused to firefly luciferase.

A dual in vitro regeneration system consisting of indirect organogenesis and somatic embryogenesis (SE), applicable to several varieties of tomato— Solanum lycopersicum (cv. Riogrande , cv. Roma , hybrid 17905 and model cv. M82 ) has been established. This system is both improved and highly reproducible compared to current methods. Callus initiation, plant regeneration and SE was developed for one-week-old cotyledon explants. Indirect organogenesis via callus induction (CI) was developed for all four varieties of tomato used in this study. One-week-old tomato seedlings were used as a source of cotyledon and hypocotyl segments as explants. The explants were subsequently cultured on Murashige and Skoog (MS) medium supplemented with different combination and concentrations of plant growth regulators (PGRs). Substantial trends in regeneration and propagation response were observed among the varieties and treatments. For commercial varieties cvs. Riogrande and Roma , maximum CI was observed at 2 weeks in CIMT 9 (0.5 mg/L NAA, 1 mg/L BAP) and CIMT 12 (2 mg/L IAA, 2 mg/L NAA, 2 mg/L BAP, 4 mg/L KIN). However, cv. M82 responded after 4 weeks to a combination of treatments CIMT 9 (0.5 mg/L NAA + 1 mg/L BAP) and CIMT 13 (2 mg/L IAA + 2 mg/L NAA + 2 mg/L BAP + 4 mg/L ZEA) for the production of calli. Subsequent shoot and root organogenesis were optimized for all four varieties. Cv. Riogrande , exhibited fastidious in vitro regeneration potential and selected for induction of somatic embryos via SE involving novel structure: rhizoid tubers (RTBs). Numerous fine hair like rhizoids (~23/explants) were first developed from cotyledon and hypocotyl explants cultured on MS medium supplemented with 0.5 or 2 mg/L NAA at pH 4.0 in dark conditions. Further incubation of each rhizoid under light conditions on MS media supplemented with 5 mg/L TDZ or BAP at pH 4.0 led to the formation of a novel structure—rhizoid Tubers (RTBs). Thus, as evident from histology, SE in Riogrande tomato species requires a medium with pH of (4.0) and higher concentration of cytokinins (BAP/TDZ) to form on average 40–45 RTBs from both explants. Histological and morphological studies revealed that RTBs develop through different stages of embryogenesis to multiple plantlets, on MS medium with 5 mg/L TDZ/BAP at normal pH (5.8). The results obtained indicated that the induced somatic embryos of tomato with lower pH are a more efficient mode of propagation than the organogenesis with or without callus formation. The RTBs led to a complete plantlets regeneration in 45 days compared to indirect organogenesis at 60 days.

The binding behavior of graphene oxide and metal nanoparticles (Au, Pt, and Pd) was observed by UV–Vis spectroscopy, fluorescence spectroscopy, dynamic light scattering, and zeta potential. Hybrids with a fixed concentration of graphene oxide (GO) were prepared with increasing concentration of metal nanoparticles to observe the effect of binding on their spectroscopic properties, size, and zeta potential. An increase in the absorption spectra of GO after binding with nanoparticles and a gradual decrease in fluorescence emission intensity with increasing concentration of nanoparticles was observed, representing their effective binding. Stern–Volmer plots differentiated the quenching constants of these nanoparticles, where Au shows the lowest and Pd shows the highest quenching among these nanoparticles. The initial hybrids showed more size change as compared to hybrids with a higher concentration of nanoparticles, whereas initial hybrids have charge similar to that of GO and gradual increase in the concentration of nanoparticles bring the charge near to the respective charge of nanoparticles. To the best of our understanding, this is the first report of its kind to study the binding interactions of two different moieties by studying changes occurred in the hydrodynamic radius and zeta potential of hybrids by titration experiments, having applications in surface treatment, drug delivery, and as sensors for environmental pollutants or other classes of organic molecules, etc.

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10An improved and highly reproducible system for invitro regeneration via somatic 11 embryogenesis (S.E), applicable to several varieties of tomato (cv. Riogrande, cv. Roma 12 grande, hybrid 17905 and model cv. M82) has been developed. First, we developed a 13 conventional indirect organogenesis for all four varieties used in this study. The 14 cotyledons and hypocotyls of 6-day-old tomato were used as explants (1-2 cm) for callus 15 induction (CI) on different callus induction media (CIM) T 0 -T 12 (6-Benzylaminopurine 16 BAP, NAA Naphthalene acetic acid, ZEA Zeatin, IAA Indole-3-acetic acid, KIN 17 Kinetin). Maximum CI response was seen on CIMT 6 (0.5 mg/L NAA, 1 mg/L BAP) and 18 CIMT 7 (2 mg/L IAA, 2 mg/L NAA, 2 mg/L BAP, 4mg/L KIN) in a period of 2 weeks 19 for commercial varieties cvs. Riogrande and Roma. However, cv. M82 responded after 4 20 weeks to a combination of treatments [CIMT 6 (0.5 mg/L NAA + 1 mg/L BAP) and 21 CIMT 8 (2 mg/L IAA + 2 mg/L NAA + 2 mg/L BAP + 4 mg/L ZEA)] for the production 22 of calli. The Riogrande, being the most responsive commercial variety, was selected for 23 invitro morphogenesis via S.E. During S.E. young cotyledons and hypocotyls explants 24 were tested on media with different ranges of pH (3 -7) supplemented with 0.5 and 2 25 mg/L NAA. Resultantly, numerous rhizoids (~38) were produced from each explant at 2 26 pH4 in dark conditions. Further incubation of each rhizoid under light conditions led to 27 the formation of a novel structure -rhizoid tubers (RTBs) on MS media supplemented 28 with 5 mg/L TDZ/BAP at pH4. We observed that only lower pH-induced rhizoids and 29 RTBs regenerated into multiple individual shoots on media at normal pH (5.8). The RTBs 30 led to a complete plantlets regeneration in 45 days compared to the conventional invitro 31 morphogenesis (60 days).32

The mutation prone RNA genome of Papaya ringspot virus could be a driving force behind its geographical spread and dissemination. Here we present the molecular investigations on atypical PRSV–P strain identified from Pakistan with genome sequence phylogenetic and recombination analysis. The PRSV-P, Pakistan outbreak strain showing a geographic spread across India and Bangladesh in phylogenetic lineage. In major recombination events, it has acquired genome variation in amino terminal of PRSV coat protein gene, whereas the gene for helper component-proteinase (HC–Pro), a nonstructural coding region of multi-domain provenance, also evolves at nucleotide and amino acid levels. The phylogenetic analysis of another highly variable P1 region showed evolutionary dynamics with respect to other geographical strains, particularly the Indian isolate from North East region (Meghalaya). PRSV–PK holds high levels of genetic divergence in comparison to American, Australian and Asian isolates. The genetic and phylogeographic analyses indicate that a spatial recombination has occurred from first PRSV, however temporal evolution is within the region of occurrence. The genetic variations and evolutionary dynamics of this virus may challenge the resistance developed in papaya against PRSV and give rise to virus lineage because of its atypical emergence where geographic spread is already occurring.

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