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At the Edges of Photosynthetic Metabolic Plasticity-On the Rapidity and Extent of Changes Accompanying Salinity Stress-Induced CAM Photosynthesis Withdrawal.

ABSTRACT: The common ice plant (Mesembryanthemum crystallinum L.) is a facultative crassulacean acid metabolism (CAM) plant, and its ability to recover from stress-induced CAM has been confirmed. We analysed the photosynthetic metabolism of this plant during the 72-h response period following salinity stress removal from three perspectives. In plants under salinity stress (CAM) we found a decline of the quantum efficiencies of PSII (Y(II)) and PSI (Y(I)) by 17% and 15%, respectively, and an increase in nonphotochemical quenching (NPQ) by almost 25% in comparison to untreated control. However, 48 h after salinity stress removal, the PSII and PSI efficiencies, specifically Y(II) and Y(I), elevated nonphotochemical quenching (NPQ) and donor side limitation of PSI (Y_ND), were restored to the level observed in control (C₃ plants). Swelling of the thylakoid membranes, as well as changes in starch grain quantity and size, have been found to be components of the salinity stress response in CAM plants. Salinity stress induced an over 3-fold increase in average starch area and over 50% decline of average seed number in comparison to untreated control. However, in plants withdrawn from salinity stress, during the first 24 h of recovery, we observed chloroplast ultrastructures closely resembling those found in intact (control) ice plants. Rapid changes in photosystem functionality and chloroplast ultrastructure were accompanied by the induction of the expression (within 24 h) of structural genes related to the PSI and PSII reaction centres, including PSAA, PSAB, PSBA (D₁), PSBD (D₂) and cp43. Our findings describe one of the most flexible photosynthetic metabolic pathways among facultative CAM plants and reveal the extent of the plasticity of the photosynthetic metabolism and related structures in the common ice plant.

SUBMITTER: Nosek M

PROVIDER: S-EPMC8395101 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:PurposePreviously we showed that epithelial cell adhesion molecule (Ep-CAM), a cell surface molecule, was highly expressed in primary retinoblastoma tumors. In the present study, we studied the genes regulated by Ep-CAM in a retinoblastoma Y79 cell line in vitro using a combination of short interference RNA and microarray technology.MethodsFlow cytometry, quantitative reverse transcriptase PCR (Q-RT-PCR), and immunohistochemistry were performed to confirm the Ep-CAM re-expression in the Y79 cells treated with 5'-azacytidine (AZC). Ep-CAM expression in AZC-treated Y79 cells was silenced using synthetic anti-Ep-CAM short interference RNA, and whole genome microarray was performed to determine the gene expression changes post Ep-CAM knockdown. Ep-CAM inhibition was confirmed by Q-RT-PCR, western blotting, and immunofluorescence.ResultsEp-CAM expression was significantly restored in Y79 cells on day 5 of AZC treatment. Ep-CAM inhibition significantly affected Y79 cell proliferation. We identified 465 upregulated genes (>or=1.0 fold) and 205 downregulated genes (<or=0.5 fold) in response to knockdown of Ep-CAM. These genes regulate several aspects of tumor function, including cell survival/proliferation, DNA replication/transcription, apoptosis, and angiogenesis. Quantitative pathway analysis using Biointerpreter further revealed that the most pronounced effect of Ep-CAM knockdown was deregulation of pathways that include mitogen-activated protein kinase (MAP) kinase and tumor protein 53 (P53) pathways. Real-time Q-RT-PCR confirmed microarray gene expression changes for selected genes.ConclusionsEp-CAM silencing significantly decreases Y79 cell proliferation and revealed a wide network of deregulated pathways in vitro. Future studies targeting Ep-CAM gene expression in vivo will help to delineate the mechanisms associated with Ep-CAM gene function in neoplastic transformation and define the potential for Ep-CAM-based molecular intervention in retinoblastoma patients.

Project description:BackgroundOver the past decades, the structural and functional genomics of rice have been deeply studied, and high density of molecular genetic markers have been developed. However, the genetic variation in leaf photosynthesis, the most important trait for rice yield improvement, was rarely studied. The lack of photosynthesis phenotyping tools is one of the bottlenecks, as traditional direct photosynthesis measurements are very low-throughput, and recently developed high-throughput methods are indirect measurements. Hence, there is an urgent need for a fast, accurate and direct measurement approach.ResultWe reported a fast photosynthesis measurement (FPM) method for phenotyping photosynthetic capacity of rice, which measures photosynthesis of excised tillers in environment-controlled lab conditions. The light response curves measured using FPM approach coped well with that the curves measured using traditional gas exchange approach. Importantly, the FPM technique achieved an average throughput of 5.4 light response curves per hour, which was 3 times faster than the 1.8 light response curves per hour using the traditional method. Tillers sampled at early morning had the highest photosynthesis, stomatal conductance and the lowest variability. In addition, even 12 h after sampling, there was no significant difference of photosynthesis rate between excised tillers and in situ. We finally investigated the genetic variations of photosynthetic traits across 568 F2 lines using the FPM technique and discussed the logistics of screening several hundred samples per day per instrumental unit using FPM to generate a wealth of photosynthetic phenotypic data, which might help to improve the selection power in large populations of rice with the ultimate aim of improving yield through improved photosynthesis.ConclusionsHere we developed a high-throughput method that can measure the rice leaf photosynthetic capacity approximately 10 times faster than traditional gas exchange approaches. Importantly, this method can overcome measurement errors caused by environmental heterogeneity under field conditions, and it is possible to measure 12 or more hours per day under lab conditions.

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At the Edges of Photosynthetic Metabolic Plasticity-On the Rapidity and Extent of Changes Accompanying Salinity Stress-Induced CAM Photosynthesis Withdrawal.

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