Jelli Venkatesh

Chlorophyll-a fluorescence evaluation of PEG-induced osmotic stress on PSII activity in Arabidopsis plants expressing SIP1

Abstract In this study, we evaluated the effect of osmotic stress on photosynthetic machinery of Arabidopsis plants expressing a gene encoding small basic intrinsic protein (SIP1) isolated from Solanum tuberosum. Intact leaves of SIP Arabidopsis plants were exposed to 15% polyethylene glycol (PEG) solution and fast Chlorophyll-a (Chl-a) fluorescence induction kinetics was measured. Photosynthetic parameters like ratio of variable and maximum fluorescence (FV/FM), absorbance of photons per active reaction center (ABS/RC), trapping of photons per active reaction center (TRo/RC), electron transport per active reaction center (ETo/RC), and performance index (PI) were measured. Furthermore, the energy pipeline model was deduced in response to PEG stress. The membrane model includes a visualization of the average “antenna size”, which follows the value of the ABS/RC. Analysis of SIP Arabidopsis plants under PEG stress through fast Chl-a fluorescence transient showed that the damage caused due to PEG is more prominent at the donor side rather than the acceptor side of PSII. Higher PI in SIP plants under PEG stress indicated a better vitality than control plants. Overall, these results indicate that constitutive expression of SIP1 in Arabidopsis plants induces significant changes in the photosynthetic machinery under PEG-induced osmotic stress.

A rich source of potential bioactive compounds with anticancer activities by Catharanthus roseus cambium meristematic stem cell cultures

ETHNOPHARMACOLOGICAL IMPORTANCE Catharanthus roseus (L.) G. Don. is an important medicinal plant with rich sources of remarkable health benefits consisting more than 100 alkaloids and significant amounts of bioactive compounds, which have been widely used as a folk medicine for treatment of several pathologies. THE AIM OF THE STUDY In the present study, we isolated and cultured innately undifferentiated cambium meristematic cells (CMCs), which were observed stable cell growth, enhancement of bioactive compounds from C.roseus. MATERIALS AND METHODS We attempted to determine the effect of association between time-course growth rates, bioactive compounds and terpenoids indole alkaloid (TIA) contents as well as antioxidant and anticancer efficacies of C. roseus CMC suspension culture treated by UV-C. RESULTS The bioactive compounds, vincristine contents, and antioxidant power were noticed significantly higher in 60 min exposure at 5 cm distances and with the directly collected sample (T7). A similar trend has also been noticed from the anticancer activity. Demonstration of TIA accumulation was found higher at 5 min exposure, at 20 cm distances and 48 h of incubation (T21) and the result of TIA contents had the highest correlation effects of anticancer activities. CONCLUSION In the current study, we demonstrated that UV-C light could enhance the production of the essential compounds and bioactivities in the CMCs of C. roseus, and thus, C. roseus CMCs have the potential to serve as an industrial platform for the production of bioactive alkaloids and antioxidant, anticancer activity. Moreover, additional efforts should be made to irradiate CMC suspension cultures from C. roseus with UV-C to achieve better pharmacological profiles.

Development of Bi gene-based SNP markers for genotyping for bitter-free cucumber lines

High contents of cucurbitacin compounds result in a bitter taste in cucumbers. The Bi locus mapped to chromosome 6 is responsible for cucumber bitterness. The Bi gene encodes oxidosqualene cyclase, a key enzyme in the cucurbitacin biosynthetic pathway. Two alleles of the Bi gene responsible for the phenotypic variation in bitterness differ by a single point mutation in the coding region. An efficient genotyping system is necessary to allow breeders to screen for bitterness alleles in their breeding programs. In the present study, the single nucleotide polymorphism located within the Bi gene, which is directly linked to cucumber bitterness, was utilized for gene-based marker development. We developed reliable and cost-effective high-resolution melting (HRM)- and Kompetitive Allele-Specific PCR (KASP)-based molecular markers (BiHRM1 and Bi-KASP). These gene-based markers should enhance the accuracy and effectiveness of marker-assisted selection for bitter-free cucumber lines in cucumber breeding programs.

Genome-Wide Analysis and Evolution of the Pto-Like Protein Kinase (PLPK) Gene Family in Pepper.

The tomato Pto gene, which encodes a serine/threonine kinase (STK) domain-containing protein, confers resistance to bacterial speck disease caused by Pseudomonas syringae pv. tomato (Pst). In this study, in vivo recognition assays using PVX constructs showed that AvrPto was specifically recognized in the pepper genotypes. This AvrPto recognition caused a nonhost hypersensitive response (HR) and localization of the PVX::AvrPto fusion protein to inoculated pepper leaf tissues, which indicates the presence of a similar Pto recognition mechanism in pepper as in tomato. However, genome-wide analysis in pepper revealed no Pto clade corresponding to that in tomato, suggesting an alternative system for Pto recognition in pepper. Nevertheless, 25 Pto-like protein kinases (PLPKs) with a highly conserved STK domain have been identified in the pepper genome. For the majority of the amino acid sites in the STK domain of Ptos and PLPKs, nonsynonymous (dN) to synonymous (dS) nucleotide substitution ratios (ω) were less than one, suggesting that purifying selection played a predominant role in the evolutionary process. However, some amino acid sites were found to be subjected to episodic positive selection in the course of evolution of Pto homologs, and, thus, different evolutionary processes might have shaped the Pto gene family in plants. Based on RNA-seq data, PLPK genes and other Pto pathway genes, such as Prf, Pti1, Pti5, and Pti6 were expressed in all tested pepper genotypes. Therefore, the nonhost HR against Pst in pepper may be due to the recognition of the AvrPto effector by a PLPK homolog, and subsequent action of downstream components of the Pto signaling pathway. However, the possibility remains that the recognition of AvrPto in pepper plants may involve activities of other receptor like kinases (RLKs). The identification of the PLPKs in this study will serve as a foundation for further efforts to understand the roles of PLPKs in nonhost resistance.