Tumor Microbiome Diversity and Composition Influence Pancreatic Cancer Outcomes.

Most patients diagnosed with resected pancreatic adenocarcinoma (PDAC) survive less than 5 years, but a minor subset survives longer. Here, we dissect the role of the tumor microbiota and the immune system in influencing long-term survival. Using 16S rRNA gene sequencing, we analyzed the tumor microbiome composition in PDAC patients with short-term survival (STS) and long-term survival (LTS). We found higher alpha-diversity in the tumor microbiome of LTS patients and identified an intra-tumoral microbiome signature (Pseudoxanthomonas-Streptomyces-Saccharopolyspora-Bacillus clausii) highly predictive of long-term survivorship in both discovery and validation cohorts. Through human-into-mice fecal microbiota transplantation (FMT) experiments from STS, LTS, or control donors, we were able to differentially modulate the tumor microbiome and affect tumor growth as well as tumor immune infiltration. Our study demonstrates that PDAC microbiome composition, which cross-talks to the gut microbiome, influences the host immune response and natural history of the disease.

A streamlined CRISPR workflow to introduce mutations and generate isogenic iPSCs for modeling amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis (ALS) represents a complex neurodegenerative disorder with significant genetic heterogeneity. To date, both the genetic etiology and the underlying molecular mechanisms driving this disease remain poorly understood, although in recent years several studies have highlighted a number of genetic mutations causative for ALS. With these mutations pointing to potential pathways that may be affected within individuals with ALS, having the ability to generate human neurons and other disease relevant cells containing these mutations becomes even more critical if new therapies are to emerge. Recent developments with the advent of induced pluripotent stem cells (iPSCs) and clustered regularly interspaced short palindromic repeats (CRISPR) gene editing fields gave us the tools to introduce or correct a specific mutation at any site within the genome of an iPSC, and thus model the specific contribution of risk mutations. In this study we describe a rapid and efficient way to either introduce a mutation into a control line, or to correct an allele-specific mutation, generating an isogenic control line from patient-derived iPSCs with a given mutation. The mutations introduced were the G94A (also known as G93A) mutation into SOD1 or H517Q into FUS, and the mutation corrected was a patient iPSC line with I114T mutation in SOD1. A combination of small molecules and growth factors were used to guide a stepwise differentiation of the edited cells into motor neurons in order to demonstrate that disease-relevant cells could be generated for downstream applications. Through a combination of iPSCs and CRISPR editing, the cells generated here will provide fundamental insights into the molecular mechanisms underlying neuron degeneration in ALS.

A Pathogenic Variant Reclassified to the Pseudogene PMS2P1 in a Patient with Suspected Hereditary Cancer.

The PMS2 gene is involved in DNA repair by the mismatch repair pathway. Deficiencies in this mechanism have been associated with Lynch Syndrome (LS), which is characterized by a high risk for colorectal, endometrial, ovarian, breast, and other cancers. Germinal pathogenic variants of PMS2 are associated with up to 5% of all cases of LS. The prevalence is overestimated for the existence of multiple homologous pseudogenes. We report the case of a 44-year-old woman diagnosed with breast cancer at 34 years without a relevant cancer family history. The presence of pathogenic variant NM_000535.7:c.1A > T, (p.Met1Leu) in PMS2 was determined by next-generation sequencing analysis with a panel of 322 cancer-associated genes and confirmed by capillary sequencing in the patient. The variant was determined in six family members (brothers, sisters, and a son) and seven non-cancerous unrelated individuals. Analysis of the amplified region showed high homology of PMS2 with five of its pseudogenes. We determined that the variant is associated with the PMS2P1 pseudogene following sequence alignment analysis. We propose considering the variant c.1A > T, (p.Met1Leu) in PMS2 for reclassification as not hereditary cancer-related, given the impact on the diagnosis and treatment of cancer patients and families carrying this variant.

Mutational Landscape of Bladder Cancer in Mexican Patients: KMT2D Mutations and chr11q15.5 Amplifications Are Associated with Muscle Invasion.

Bladder cancer (BC) is the most common neoplasm of the urinary tract, which originates in the epithelium that covers the inner surface of the bladder. The molecular BC profile has led to the development of different classifications of non-muscle invasive bladder cancer (NMIBC) and muscle-invasive bladder cancer (MIBC). However, the genomic BC landscape profile of the Mexican population, including NMIBC and MIBC, is unknown. In this study, we aimed to identify somatic single nucleotide variants (SNVs) and copy number variations (CNVs) in Mexican patients with BC and their associations with clinical and pathological characteristics. We retrospectively evaluated 37 patients treated between 2012 and 2021 at the National Cancer Institute-Mexico (INCan). DNA samples were obtained from paraffin-embedded tumor tissues and exome sequenced. Strelka2 and Lancet packages were used to identify SNVs and insertions or deletions. FACETS was used to determine CNVs. We found a high frequency of mutations in TP53 and KMT2D, gains in 11q15.5 and 19p13.11-q12, and losses in 7q11.23. STAG2 mutations and 1q11.23 deletions were also associated with NMIBC and low histologic grade.

Comparison of satisfaction degree of patients treated at the Inflammatory Bowel Disease Unit (IBDU) of Hospital Universitario 12 de Octubre between previous face-to-face care and telephone care during the COVID-19 pandemic.

The aim of the IBDU is to provide comprehensive care for patients with IBD (1,2). During the COVID-19 pandemic, telephone medical consultations and telemedicine training sessions were implemented to ensure patient safety (3). The aim of this study was to determine whether there was a difference in the degree of satisfaction between face-to-face and telephone care, as well as in the annual patient sessions.

Inflammatory bowel disease and solid organ transplantation.

The population of patients with inflammatory bowel disease (IBD) and solid organ transplant (SOT) is increasing. Two clinical scenarios exist, recurrence of pre-existing IBD, which is more common, and de novo development of IBD, with a much higher incidence than in the general population. Their clinical course differs and may have a negative impact on the graft in both cases. The pathophysiological mechanisms remain unknown and no specific treatment recommendations are available. The combined effect of biologic therapy against IBD and immunosuppressive therapy against a potential rejection means that close monitoring is mandatory to identify infection, autoimmune events and malignancies. The colorectal cancer (CRC) rate is higher in this population. The group at greatest risk are patients with IBD undergoing liver transplantation (LT) for primary sclerosing cholangitis (PSC).

Development and economic evaluation of an eco-friendly biocatalytic synthesis of emollient esters.

During the past decades the understanding and prospects of enzyme-catalysed reactions have been massively widened and there are a number of implemented large-scale enzymatic processes mainly based in the use of commercial biocatalysts. As it might happen that the same process can be successfully carried out by different commercial lipases, the election of the biocatalyst must rely on productivity and economic considerations. This work presents productiveness and direct operation cost evaluation as a key tool for the selection between two commercial lipase catalysts, the versatile but expensive Novozym® 435 and a much more economical option, Lipozyme® TL IM, in the synthesis of spermaceti, a mixture of emollient esters with cosmetic applications. Proving that Novozym® 435 leads to minimum savings of 10% with respect to the cheapest immobilized derivative, biocatalyst cost does not appear to be the major contribution to the economics of the processes under study, due to their great capacity to be recovered and reused. At laboratory scale, the biggest economic investment is caused by substrates, which can be massively reduced at industrial scale by using bulk reagents. In such case, energy cost may be the major contribution to the process economy. This work proposes an optimized process ready to be scaled-up in order to accurately determine the energetic requirements of the possible industrial enzymatic synthesis.

Immune Cell Production of Interleukin 17 Induces Stem Cell Features of Pancreatic Intraepithelial Neoplasia Cells.

BACKGROUND & AIMS: Little is known about how the immune system affects stem cell features of pancreatic cancer cells. Immune cells that produce interleukin 17A (IL17A) in the chronically inflamed pancreas (chronic pancreatitis) contribute to pancreatic interepithelial neoplasia (PanIN) initiation and progression. We investigated the effects that IL17A signaling exerts on pancreatic cancer progenitor cells and the clinical relevance of this phenomena. METHODS: We performed studies with Mist1Cre;LSLKras;Rosa26mTmG (KCiMist;G) and Kras(G12D);Trp53(R172H);Pdx1-Cre (KPC) mice (which upon tamoxifen induction spontaneously develop PanINs) and control littermates. Some mice were injected with neutralizing antibodies against IL17A or control antibody. Pancreata were collected, PanIN epithelial cells were isolated by flow cytometry based on lineage tracing, and gene expression profiles were compared. We collected cells from pancreatic tumors of KPC mice, incubated them with IL17 or control media, measured expression of genes regulated by IL17 signaling, injected the cancer cells into immune competent mice, and measured tumor growth. IL17A was overexpressed in pancreata of KCiMist mice from an adenoviral vector. Pancreata were collected from all mice and analyzed by histology and immunohistochemistry. Levels of DCLK1 and other proteins were knocked down in KPC pancreatic cancer cells using small interfering or short hairpin RNAs; cells were analyzed by immunoblotting. We obtained 65 pancreatic tumor specimens from patients, analyzed protein levels by immunohistochemistry, and compared results with patient survival times. We also analyzed gene expression levels and patient outcome using The Cancer Genome Atlas database. RESULTS: PanIN cells from KCiMist;G mice had a gene expression pattern associated with embryonic stem cells. Mice given injections of IL17-neutralizing antibodies, or with immune cells that did not secrete IL17, lost this expression pattern and had significantly decreased expression of DCLK1 and POU2F3, which regulate tuft cell development. KCiMist mice that overexpressed IL17 formed more PanINs, with more DCLK1-positive cells, than control mice. Pancreatic tumor cells from KPC mice and human Capan-2 cells exposed to IL17A had increased activation of NF-κB and mitogen-activated protein kinase signaling and increased expression of DCLK1 and ALDH1A1 (a marker of embryonic stem cells) compared with cells in control media. These cells also formed tumors faster that cells not exposed to IL17 when they were injected into immunocompetent mice. KPC cells with knockdown of DCLK1 expressed lower levels of ALDH1A1 after incubation with IL17 than cells without knockdown. Expression of the IL17 receptor C was higher in DCLK1-positive PanIN cells from mice compared with DCLK1-negative PanIN cells. In human pancreatic tumor tissues, high levels of DCLK1 associated with a shorter median survival time of patients (17.7 months, compared with 26.6 months of patients whose tumors had low levels of DCLK1). Tumor levels of POU2F3 and LAMC2 were also associated with patient survival time. CONCLUSIONS: In studies of mouse and human pancreatic tumors and precursors, we found that immune cell-derived IL17 regulated development of tuft cells and stem cell features of pancreatic cancer cells via increased expression of DCLK1, POU2F3, ALDH1A1, and IL17RC. Strategies to disrupt this pathway might be developed to prevent pancreatic tumor growth and progression.

Infliximab Dose Escalation as an Effective Strategy for Managing Secondary Loss of Response in Ulcerative Colitis.

BACKGROUND: The outcomes of infliximab dose escalation in ulcerative colitis (UC) have not been well evaluated. AIMS: To assess the short- and long-term outcomes of infliximab dose escalation in a cohort of patients with UC. METHODS: This was a multicenter, retrospective, cohort study. All consecutive UC patients who had lost response to infliximab maintenance infusions and who underwent infliximab dose escalation were included. Post-escalation short-term clinical response and remission were evaluated. In the long term, the cumulative probabilities of infliximab failure-free survival and colectomy-free survival were calculated. Predictors of short-term response and event-free survival were estimated using logistic regression analysis and Cox proportional hazard regression analysis. RESULTS: Seventy-nine patients were included. Fifty-four patients (68.4%) achieved short-term clinical response and 41 patients (51.9%) entered in clinical remission. After a median follow-up of 15 months [interquartile range (IQR) 8-26], 33 patients (41.8%) had infliximab failure. Patients with short-term response had a significantly lower adjusted rate of infliximab failure [hazard ratio (HR) 0.24, 95% confidence interval (CI) 0.12-0.49; p < 0.001]. During a median follow-up of 24 months (IQR 13-34), 9 patients (11.4%) needed colectomy. Short-term response was identified as a predictor of colectomy avoidance (HR 0.14; 95% CI 0.03-0.69; p < 0.007). CONCLUSIONS: In UC patients who lost response to infliximab during maintenance, infliximab dose escalation enabled recovery of short-term response in nearly 70% of patients. In the long term, 58% of patients maintained sustained clinical benefit, and 9 of 10 avoided colectomy. Short-term response was associated with an 86% reduction in the relative risk of colectomy.

MutS HOMOLOG1 is a nucleoid protein that alters mitochondrial and plastid properties and plant response to high light.

Mitochondrial-plastid interdependence within the plant cell is presumed to be essential, but measurable demonstration of this intimate interaction is difficult. At the level of cellular metabolism, several biosynthetic pathways involve both mitochondrial- and plastid-localized steps. However, at an environmental response level, it is not clear how the two organelles intersect in programmed cellular responses. Here, we provide evidence, using genetic perturbation of the MutS Homolog1 (MSH1) nuclear gene in five plant species, that MSH1 functions within the mitochondrion and plastid to influence organellar genome behavior and plant growth patterns. The mitochondrial form of the protein participates in DNA recombination surveillance, with disruption of the gene resulting in enhanced mitochondrial genome recombination at numerous repeated sequences. The plastid-localized form of the protein interacts with the plastid genome and influences genome stability and plastid development, with its disruption leading to variegation of the plant. These developmental changes include altered patterns of nuclear gene expression. Consistency of plastid and mitochondrial response across both monocot and dicot species indicate that the dual-functioning nature of MSH1 is well conserved. Variegated tissues show changes in redox status together with enhanced plant survival and reproduction under photooxidative light conditions, evidence that the plastid changes triggered in this study comprise an adaptive response to naturally occurring light stress.

Study of different reaction schemes for the enzymatic synthesis of polyglycerol polyricinoleate.

BACKGROUND: Different strategies for the solvent-free enzymatic production of polyglycerol polyricinoleate (PGPR) were explored in an attempt to simplify and improve the process. Besides the conventional procedure (obtaining polyricinoleic acid, followed by its esterification with polyglycerol), two alternative methods are proposed: (1) reversing the synthesis order, i.e. esterification of polyglycerol with ricinoleic acid and then the condensation of ricinoleic acid with the previously obtained polyglycerol ester; and (2) the enzymatic synthesis of PGPR in a single-step process. RESULTS: The reaction sequences were carried out in an open-air reactor with free and immobilised lipases (triacylglycerol acylhydrolases, E.C. 3.1.1.3): Candida rugosa lipase to obtain polyricinoleic acid and Rhizopus oryzae lipase for the esterification of polyglycerol with the carboxyl group of ricinoleic or polyricinoleic acid. A co-immobilised derivative containing both lipases was used to catalyse the single-stage scheme. The three processes were carried out in a vacuum reactor, obtaining in every case PGPR that complied with the legal specifications of the European Community and recommendations provided in the Food Chemical Codex. CONCLUSION: The results demonstrate that all three protocols are viable for the enzymatic synthesis of PGPR and require similar reaction times. The single-stage scheme is easier to carry out.

Impact of Standard Versus Low Pneumoperitoneum Pressure on Peritoneal Environment in Laparoscopic Cholecystectomy. Randomized Clinical Trial.

BACKGROUND: High CO 2 pneumoperitoneum pressure during laparoscopy adversely affects the peritoneal environment. This study hypothesized that low pneumoperitoneum pressure may be linked to less peritoneal damage and possibly to better clinical outcomes. MATERIALS AND METHODS: One hundred patients undergoing scheduled laparoscopic cholecystectomy were randomized 1:1 to low or to standard pneumoperitoneum pressure. Peritoneal biopsies were performed at baseline time and 1 hour after peritoneum insufflation in all patients. The primary outcome was peritoneal remodeling biomarkers and apoptotic index. Secondary outcomes included biomarker differences at the studied times and some clinical variables such as length of hospital stay, and quality and safety issues related to the procedure. RESULTS: Peritoneal IL6 after 1 hour of surgery was significantly higher in the standard than in the low-pressure group (4.26±1.34 vs. 3.24±1.21; P =0.001). On the contrary, levels of connective tissue growth factor and plasminogen activator inhibitor-I were higher in the low-pressure group (0.89±0.61 vs. 0.61±0.84; P =0.025, and 0.74±0.89 vs. 0.24±1.15; P =0.028, respectively). Regarding apoptotic index, similar levels were found in both groups and were 44.0±10.9 and 42.5±17.8 in low and standard pressure groups, respectively. None of the secondary outcomes showed differences between the 2 groups. CONCLUSIONS: Peritoneal inflammation after laparoscopic cholecystectomy is higher when surgery is performed under standard pressure. Adhesion formation seems to be less in this group. The majority of patients undergoing surgery under low pressure were operated under optimal workspace conditions, regardless of the surgeon's expertise.

New-onset diabetes is a predictive risk factor for pancreatic lesions in high-risk individuals: An observational cohort study.

Background and Objectives: Pancreatic cancer (PC) is the third cause of cancer-related deaths. Early detection and interception of premalignant pancreatic lesions represent a promising strategy to improve outcomes. We evaluated risk factors of focal pancreatic lesions (FPLs) in asymptomatic individuals at hereditary high risk for PC. Methods: This is an observational single-institution cohort study conducted over a period of 5 years. Surveillance was performed through imaging studies (EUS or magnetic resonance imaging/magnetic resonance cholangiopancreatography) and serum biomarkers. We collected demographic characteristics and used univariate and multivariate logistic regression models to evaluate associations between potential risk factors and odd ratios (ORs) for FPL development. Results: A total of 205 patients completed baseline screening. Patients were followed up to 53 months. We detected FPL in 37 patients (18%) at baseline; 2 patients had lesions progression during follow-up period, 1 of them to PC. Furthermore, 13 patients developed new FPLs during the follow-up period. Univariate and multivariate analyses revealed that new-onset diabetes (NOD) is strongly associated with the presence of FPL (OR, 10.94 [95% confidence interval, 3.01-51.79; P < 0.001]; OR, 9.98 [95% confidence interval, 2.15-46.33; P = 0.003]). Follow-up data analysis revealed that NOD is also predictive of lesions progression or development of new lesions during screening (26.7% vs. 2.6%; P = 0.005). Conclusions: In a PC high-risk cohort, NOD is significantly associated with presence of FPL at baseline and predictive of lesions progression or new lesions during surveillance.

BatFly: A database of Neotropical bat-fly interactions.

Global changes have increased the risk of emerging infectious diseases, which can be prevented or mitigated by studying host-parasite interactions, among other measures. Bats and their ectoparasitic flies of the families Streblidae and Nycteribiidae are an excellent study model but, so far, our knowledge has been restricted to fragmented records at a local scale. To help boost research, we assembled a data set of bat-fly interactions from 174 studies published between 1904 and 2022 plus three original data sets. Altogether, these studies were carried out at 650 sites in the Neotropics, mainly distributed in Mexico, Brazil, Argentina, southern USA, and Colombia, among other countries. In total, our data set contains 3984 interaction records between 237 bat species and 255 fly species. The bat species with the largest number of recorded interactions were Carollia perspicillata (357), Artibeus jamaicensis (263), and Artibeus lituratus (228). The fly species with the largest number of recorded interactions were Trichobius joblingi (256), Megistopoda aranea (235), and Megistopoda proxima (215). The interaction data were extracted, filtered, taxonomically harmonized, and made available in a tidy format together with linked data on bat population, fly population, study reference, sampling methods and geographic information from the study sites. This interconnected structure enables the expansion of information for each interaction record, encompassing where and how each interaction occurred, as well as the number of bats and flies involved. We expect BatFly to open new avenues for research focused on different levels of ecological organization and spatial scales. It will help consolidate knowledge about ecological specialization, resource distribution, pathogen transmission, and the drivers of parasite prevalence over a broad spatial range. It may also help to answer key questions such as: Are there differences in fly prevalence or mean infestation across Neotropical ecoregions? What ecological drivers explain those differences? How do specialization patterns vary among fly species in the Neotropics? Furthermore, we expect BatFly to inspire research aimed at understanding how climate and land-use changes may impact host-parasite interactions and disease outbreaks. This kind of research may help us reach Sustainable Development Goal 3, Good Health and Wellbeing, outlined by the United Nations. The data are released under a Creative Commons Attribution 4.0 International License.

Homozygous ALS-linked mutations in TARDBP/TDP-43 lead to hypoactivity and synaptic abnormalities in human iPSC-derived motor neurons.

Cytoplasmic mislocalization and aggregation of the RNA-binding protein TDP-43 is a pathological hallmark of the motor neuron (MN) disease amyotrophic lateral sclerosis (ALS). Furthermore, while mutations in TARDBP (encoding TDP-43) have been associated with ALS, the pathogenic consequences of these mutations remain poorly understood. Using CRISPR-Cas9, we engineered two homozygous knock-in induced pluripotent stem cell lines carrying mutations in TARDBP encoding TDP-43A382T and TDP-43G348C, two common yet understudied ALS TDP-43 variants. Motor neurons (MNs) differentiated from knock-in iPSCs had normal viability and displayed no significant changes in TDP-43 subcellular localization, phosphorylation, solubility, or aggregation compared with isogenic control MNs. However, our results highlight synaptic impairments in both TDP-43A382T and TDP-43G348C MN cultures, as reflected in synapse abnormalities and alterations in spontaneous neuronal activity. Collectively, our findings suggest that MN dysfunction may precede the occurrence of TDP-43 pathology and neurodegeneration in ALS and further implicate synaptic and excitability defects in the pathobiology of this disease.

Individualized Pain Treatment in Chronic Pancreatitis (INPAIN): An International, Multicenter, Investigator-initiated, Prospective, Cohort Study.

INTRODUCTION: Pain is the foremost complication of chronic pancreatitis (CP), affecting about 70% of patients. However, the pathophysiological understanding and management of CP-related pain is complex, likely as patients have diverse "pain phenotypes" responding differently to treatment. This study aims to develop a bedside test panel to identify distinct pain phenotypes, investigate the temporal evolution, and determine whether they can be used to predict treatment response. METHOD: The INPAIN study is an international, multi-center, observational, longitudinal cohort study comprised of 4 sub-studies. The studies will prospectively enroll 400 CP patients (50 without pain and 350 with pain) and 50 control subjects, conducting biannual observations for four years. The test panel is comprised of comprehensive subjective and objective assessment parameters. Statistical analysis strategies differ across the sub-studies. A model to predict treatment efficacy will be developed using various machine learning techniques, including an artificial intelligence approach, with internal cross-validation. Trajectories in pain parameters will be characterized by graphical analysis and mixed effect models. DISCUSSION: The INPAIN study aims to comprehensively understand pain in CP through a test panel developed for routine clinical use. This tool has the potential to personalize treatments, improve clinical practice, enhance patient care, improve quality of life, and minimize treatment side effects.

Genomic landscape of early-stage prostate adenocarcinoma in Mexican patients: an exploratory study.

BACKGROUND: Health disparities have been highlighted among patient with prostate adenocarcinoma (PRAD) due to ethnicity. Mexican men present a more aggressive disease than other patients resulting in less favorable treatment outcome. We aimed to identify the mutational landscape which could help to reduce the health disparities among minority groups and generate the first genomics exploratory study of PRAD in Mexican patients. METHODS: Paraffin-embedded formalin-fixed tumoral tissue from 20 Mexican patients with early-stage PRAD treated at The Instituto Nacional de Cancerología, Mexico City from 2017 to 2019 were analyzed. Tumoral DNA was prepared for whole exome sequencing, the resulting files were mapped against h19 using BWA-MEM. Strelka2 and Lancet packages were used to identify single nucleotide variants (SNV) and insertions or deletions. FACETS was used to determine somatic copy number alterations (SCNA). Cancer Genome Interpreter web interface was used to determine the clinical relevance of variants. RESULTS: Patients were in an early clinical stage and had a mean age of 59.55 years (standard deviation [SD]: 7.1 years) with 90% of them having a Gleason Score of 7. Follow-up time was 48.50 months (SD: 32.77) with recurrences and progression in 30% and 15% of the patients, respectively. NUP98 (20%), CSMD3 (15%) and FAT1 (15%) were the genes most frequently affected by SNV; ARAF (75%) and ZNF419 (70%) were the most frequently affected by losses and gains SNCA's. One quarter of the patients had mutations useful as biomarkers for the use of PARP inhibitors, they comprise mutations in BRCA, RAD54L and ATM. SBS05, DBS03 and ID08 were the most common mutational signatures present in this cohort. No associations with recurrence or progression were identified. CONCLUSIONS: This pilot study reveals the mutational landscape of early-stage prostate adenocarcinoma in Mexican men, providing a first approach to understand the mutational patterns and actionable mutations in early prostate cancer can inform personalized treatment approaches and reduce the underrepresentation in genomic cancer studies.

The chloroplast triggers developmental reprogramming when mutS HOMOLOG1 is suppressed in plants.

Multicellular eukaryotes demonstrate nongenetic, heritable phenotypic versatility in their adaptation to environmental changes. This inclusive inheritance is composed of interacting epigenetic, maternal, and environmental factors. Yet-unidentified maternal effects can have a pronounced influence on plant phenotypic adaptation to changing environmental conditions. To explore the control of phenotypy in higher plants, we examined the effect of a single plant nuclear gene on the expression and transmission of phenotypic variability in Arabidopsis (Arabidopsis thaliana). MutS HOMOLOG1 (MSH1) is a plant-specific nuclear gene product that functions in both mitochondria and plastids to maintain genome stability. RNA interference suppression of the gene elicits strikingly similar programmed changes in plant growth pattern in six different plant species, changes subsequently heritable independent of the RNA interference transgene. The altered phenotypes reflect multiple pathways that are known to participate in adaptation, including altered phytohormone effects for dwarfed growth and reduced internode elongation, enhanced branching, reduced stomatal density, altered leaf morphology, delayed flowering, and extended juvenility, with conversion to perennial growth pattern in short days. Some of these effects are partially reversed with the application of gibberellic acid. Genetic hemicomplementation experiments show that this phenotypic plasticity derives from changes in chloroplast state. Our results suggest that suppression of MSH1, which occurs under several forms of abiotic stress, triggers a plastidial response process that involves nongenetic inheritance.

Physiological traits related to terminal drought resistance in common bean (Phaseolus vulgaris L.).

BACKGROUND: A major problem in common bean (Phaseolus vulgaris L.) agriculture is the low yield due to terminal drought. Because common beans are grown over a broad variety of environments, the study of drought-resistant genotypes might be useful to identify distinctive or common mechanisms needed for survival and seed production under drought. RESULTS: In this study the relationship between terminal drought resistance and some physiological parameters was analysed using cultivars contrasting in their drought response from two different gene pools. Trials were performed in three environments. As expected, drought treatments induced a decrease in leaf relative humidity and an increase in leaf temperature; however, when these parameters were compared between susceptible and resistant cultivars under optimal irrigation and drought, no significant differences were detected. Similar results were obtained for chlorophyll content. In contrast, analysis of relative water content (RWC) and stomatal conductance values showed reproducible significant differences between susceptible and resistant cultivars grown under optimal irrigation and drought across the different environments. CONCLUSIONS: The data indicate that drought-resistant cultivars maximise carbon uptake and limit water loss upon drought by increasing stomatal closure during the day and attaining a higher RWC during the night as compared with susceptible cultivars, suggesting a water balance fine control to achieve enough yield under drought.