RBCS1 expression in coffee: Coffea orthologs, Coffea arabica homeologs, and expression variability between genotypes and under drought stress

Background: In higher plants, the inhibition of photosynthetic capacity under drought is attributable to stomatal and non-stomatal (i.e., photochemical and biochemical) effects. In particular, a disruption of photosynthetic metabolism and Rubisco regulation can be observed. Several studies reported reduced expression of the RBCS genes, which encode the Rubisco small subunit, under water stress. Results: Expression of the RBCS1 gene was analysed in the allopolyploid context of C. arabica, which originates from a natural cross between the C. canephora and C. eugenioides species. Our study revealed the existence of two homeologous RBCS1 genes in C. arabica: one carried by the C. canephora sub-genome (called CaCc) and the other carried by the C. eugenioides sub-genome (called CaCe). Using specific primer pairs for each homeolog, expression studies revealed that CaCe was expressed in C. eugenioides and C. arabica but was undetectable in C. canephora. On the other hand, CaCc was expressed in C. canephora but almost completely silenced in non-introgressed ("pure") genotypes of C. arabica. However, enhanced CaCc expression was observed in most C. arabica cultivars with introgressed C. canephora genome. In addition, total RBCS1 expression was higher for C. arabica cultivars that had recently introgressed C. canephora genome than for "pure" cultivars. For both species, water stress led to an important decrease in the abundance of RBCS1 transcripts. This was observed for plants grown in either greenhouse or field conditions under severe or moderate drought. However, this reduction of RBCS1 gene expression was not accompanied by a decrease in the corresponding protein in the leaves of C. canephora subjected to water withdrawal. In that case, the amount of RBCS1 was even higher under drought than under unstressed (irrigated) conditions, which suggests great stability of RBCS1 under adverse water conditions. On the other hand, for C. arabica, high nocturnal expression of RBCS1 could also explain the accumulation of the RBCS1 protein under water stress. Altogether, the results presented here suggest that the content of RBCS was not responsible for the loss of photosynthetic capacity that is commonly observed in water-stressed coffee plants. Conclusion: We showed that the CaCe homeolog was expressed in C. eugenioides and non-introgressed ("pure") genotypes of C. arabica but that it was undetectable in C. canephora. On the other hand, the CaCc homeolog was expressed in C. canephora but highly repressed in C. arabica. Expression of the CaCc homeolog was enhanced in C. arabica cultivars that experienced recent introgression with C. canephora. For both C. canephora and C. arabica species, total RBCS1 gene expression was highly reduced with WS. Unexpectedly, the accumulation of RBCS1 protein was observed in the leaves of C. canephora under WS, possibly coming from nocturnal RBCS1 expression. These results suggest that the increase in the amount of RBCS1 protein could contribute to the antioxidative function of photorespiration in water-stressed coffee plants. (Résumé d'auteur

Dynamic culturing of cartilage tissue: the significance of hydrostatic pressure

Human articular cartilage functions under a wide range of mechanical loads in synovial joints, where hydrostatic pressure (HP) is the prevalent actuating force. We hypothesized that the formation of engineered cartilage can be augmented by applying such physiologic stimuli to chondrogenic cells or stem cells, cultured in hydrogels, using custom-designed HP bioreactors. To test this hypothesis, we investigated the effects of distinct HP regimens on cartilage formation in vitro by either human nasal chondrocytes (HNCs) or human adipose stem cells (hASCs) encapsulated in gellan gum (GG) hydrogels. To this end, we varied the frequency of low HP, by applying pulsatile hydrostatic pressure or a steady hydrostatic pressure load to HNC-GG constructs over a period of 3 weeks, and evaluated their effects on cartilage tissue-engineering outcomes. HNCs (10 · 106 cells/ mL) were encapsulated in GG hydrogels (1.5%) and cultured in a chondrogenic medium under three regimens for 3 weeks: (1) 0.4MPa Pulsatile HP; (2) 0.4MPa Steady HP; and (3) Static. Subsequently, we applied the pulsatile regimen to hASC-GG constructs and varied the amplitude of loading, by generating both low (0.4 MPa) and physiologic (5 MPa) HP levels. hASCs (10x106 cells/mL) were encapsulated in GG hydrogels (1.5%) and cultured in a chondrogenic medium under three regimens for 4 weeks: (1) 0.4MPa Pulsatile HP; (2) 5MPa Pulsatile HP; and (3) Static. In the HNC study, the best tissue development was achieved by the pulsatile HP regimen, whereas in the hASC study, greater chondrogenic differentiation and matrix deposition were obtained for physiologic loading, as evidenced by gene expression of aggrecan, collagen type II, and sox-9; metachromatic staining of cartilage extracellular matrix; and immunolocalization of collagens. We thus propose that both HNCs and hASCs detect and respond to physical forces, thus resembling joint loading, by enhancing cartilage tissue development in a frequency- and amplitude-dependant manner.Fundação para a Ciência e a Tecnologia (FCT) - SFRH/BD/42316/200

Remission definitions guiding immunosuppressive therapy in rheumatoid arthritis: which is best fitted for the purpose?

Objective To assess which definition of remission best predicts good radiographic outcome (GRO) and good functional outcome (GFO) in rheumatoid arthritis, focusing the updated American College of Rheumatology/European Alliance of Associations for Rheumatology criteria. Material and methods Meta-analyses of individual patient data (IPD) from randomised controlled trials (RCTs). Six definitions of remission were considered: (1) Boolean with Patient Global Assessment (PGA)≤1 (Boolean); (2) Simplified Disease Activity Index (SDAI)≤3.3; (3) Clinical Disease Activity Index (CDAI)≤2.8; (4) Boolean with PGA≤2 (Updated-Boolean); (5) Boolean with Physician Global Assessment (PhGA≤1) replacing PGA (Boolean-PhGA) and (6) Boolean excluding PGA (3VBoolean). GRO was defined as a worsening ≤0.5 units in radiographic score and GFO as a no worsening in Health Assessment Questionnaire (HAQ), that is, †HAQ-DI≤0.0 units. Relationships between each remission definition at 6 and/or 12 months and GRO and GFO during the second year were analysed. Pooled probabilities for each outcome for each definition and their predictive accuracy were estimated. Results IPD from eight RCTs (n=4423) were analysed. Boolean, SDAI, CDAI, Updated-Boolean, Boolean-PhGA and 3VBoolean were achieved by 24%, 27%, 28%, 32%, 33% and 43% of all patients, respectively. GRO among patients achieving remission ranged from 82.4% (3VBoolean) to 83.9% (SDAI). 3VBoolean showed the highest predictive accuracy for GRO: 51.1% versus 38.8% (Boolean) and 44.1% (Updated-Boolean). The relative risk of GFO ranged from 1.16 (Boolean) to 1.05 (3VBoolean). However, the proportion of GFO correctly predicted was highest for the 3VBoolean (50.3%) and lowest for the Boolean (43.8%). Conclusion 3VBoolean definition provided the most accurate prediction of GRO and GFO, avoiding the risk of overtreatment in a substantial proportion of patients without increment in radiographic damage progression, supporting the proposal that 3VBoolean remission is preferable to guide immunosuppressive treatment. The patient's perspective, which must remain central, is best served by an additional patient-oriented target: a dual-target approach

Multiwavelength studies of MHD waves in the solar chromosphere: An overview of recent results

The chromosphere is a thin layer of the solar atmosphere that bridges the relatively cool photosphere and the intensely heated transition region and corona. Compressible and incompressible waves propagating through the chromosphere can supply significant amounts of energy to the interface region and corona. In recent years an abundance of high-resolution observations from state-of-the-art facilities have provided new and exciting ways of disentangling the characteristics of oscillatory phenomena propagating through the dynamic chromosphere. Coupled with rapid advancements in magnetohydrodynamic wave theory, we are now in an ideal position to thoroughly investigate the role waves play in supplying energy to sustain chromospheric and coronal heating. Here, we review the recent progress made in characterising, categorising and interpreting oscillations manifesting in the solar chromosphere, with an impetus placed on their intrinsic energetics.Comment: 48 pages, 25 figures, accepted into Space Science Review