A citrate efflux transporter important for manganese distribution and phosphorus uptake in rice.

The plant citrate transporters, functional in mineral nutrient uptake and homeostasis, usually belong to the multidrug and toxic compound extrusion transporter family. We identified and functionally characterized a rice (Oryza sativa) citrate transporter, OsCT1, which differs from known plant citrate transporters and is structurally close to rice silicon transporters. Domain analysis depicted that OsCT1 carries a bacterial citrate-metal transporter domain, CitMHS. OsCT1 showed citrate efflux activity when expressed in Xenopus laevis oocytes and is localized to the cell plasma membrane. It is highly expressed in the shoot and reproductive tissues of rice, and its promoter activity was visible in cells surrounding the vasculature. The OsCT1 knockout (KO) lines showed a reduced citrate content in the shoots and the root exudates, whereas overexpression (OE) line showed higher citrate exudation from their roots. Further, the KO and OE lines showed variations in the manganese (Mn) distribution leading to changes in their agronomical traits. Under deficient conditions (Mn-sufficient conditions followed by 8 days of 0 µm MnCl2 · 4H2 O treatment), the supply of manganese towards the newer leaf was found to be obstructed in the KO line. There were no significant differences in phosphorus (P) distribution; however, P uptake was reduced in the KO and increased in OE lines at the vegetative stage. Further, experiments in Xenopus oocytes revealed that OsCT1 could efflux citrate with Mn. In this way, we provide insights into a mechanism of citrate-metal transport in plants and its role in mineral homeostasis, which remains conserved with their bacterial counterparts.

Mediator complex: an important regulator of root system architecture.

Mediator, a multiprotein complex, is an important component of the transcription machinery. In plants, the latest reports from our group and some other studies have established that Mediator functions as a signal processor that conveys transcriptional signals from transcription factors to RNA polymerase II. It has been found to be involved in different developmental and stress-adaptation conditions ranging from embryo, root, and shoot development to flowering and senescence and also in response to different biotic and abiotic stresses. In the last one decade, significant progress has been made in understanding the role of Mediator subunits in root development. They have been shown to transcriptionally regulate development of almost all the components of root system architecture - primary root, lateral root and root hair. Their role has also been appreciated in nutrient acquisition through root. In this review, we have discussed all the known functions of Mediator subunits during root development. We have also highlighted the role of Mediator as a nodal point for processing different hormone signaling that regulate root morphogenesis and growth.

Root-Expressed Rice PAP3b Enhances Secreted APase Activity and Helps Utilize Organic Phosphate.

Phosphate (Pi) deficiency leads to the induction of purple acid phosphatases (PAPs) in plants, which dephosphorylate organic phosphorus (P) complexes in the rhizosphere and intracellular compartments to release Pi. In this study, we demonstrate that OsPAP3b belongs to group III low-molecular weight PAP and is low Pi-responsive, preferentially in roots. The expression of OsPAP3b is negatively regulated with Pi resupply. Interestingly, OsPAP3b was found to be dual localized to the nucleus and secretome. Furthermore, OsPAP3b is transcriptionally regulated by OsPHR2 as substantiated by DNA-protein binding assay. Through in vitro biochemical assays, we further demonstrate that OsPAP3b is a functional acid phosphatase (APase) with broad substrate specificity. The overexpression (OE) of OsPAP3b in rice led to increased secreted APase activity and improved mineralization of organic P sources, which resulted in better growth of transgenics compared to the wild type when grown on organic P as an exogenous P substrate. Under Pi deprivation, OsPAP3b knock-down and knock-out lines showed no significant changes in total P content and dry biomass. However, the expression of other phosphate starvation-induced genes and the levels of metabolites were found to be altered in the OE and knock-down lines. In addition, in vitro pull-down assay revealed multiple putative interacting proteins of OsPAP3b. Our data collectively suggest that OsPAP3b can aid in organic P utilization in rice. The APase isoform behavior and nuclear localization indicate its additional role, possibly in stress signaling. Considering its important roles, OsPAP3b could be a potential target for improving low Pi adaptation in rice.

Monogalactosyl diacylglycerol synthase 3 affects phosphate utilization and acquisition in rice.

Galactolipids are essential to compensate for the loss of phospholipids by 'membrane lipid remodelling' in plants under phosphorus (P) deficiency conditions. Monogalactosyl diacylglycerol (MGDG) synthases catalyse the synthesis of MGDG which is further converted into digalactosyl diacylglycerol (DGDG), later replacing phospholipids in the extraplastidial membranes. However, the roles of these enzymes are not well explored in rice. In this study, the rice MGDG synthase 3 gene (OsMGD3) was identified and functionally characterized. We showed that the plant phosphate (Pi) status and the transcription factor PHOSPHATE STARVATION RESPONSE 2 (OsPHR2) are involved in the transcriptional regulation of OsMGD3. CRISPR/Cas9 knockout and overexpression lines of OsMGD3 were generated to explore its potential role in rice adaptation to Pi deficiency. Compared with the wild type, OsMGD3 knockout lines displayed a reduced Pi acquisition and utilization while overexpression lines showed an enhancement of the same. Further, OsMGD3 showed a predominant role in roots, altering lateral root growth. Our comprehensive lipidomic analysis revealed a role of OsMGD3 in membrane lipid remodelling, in addition to a role in regulating diacylglycerol and phosphatidic acid contents that affected the expression of Pi transporters. Our study highlights the role of OsMGD3 in affecting both internal P utilization and P acquisition in rice.

Organic acids: versatile stress-response roles in plants.

Organic acids (OAs) are central to cellular metabolism. Many plant stress responses involve the exudation of OAs at the root-soil interface, which can improve soil mineral acquisition and toxic metal tolerance. Because of their simple structure, the low-molecular-weight OAs are widely studied. We discuss the conventional roles of OAs, and some newly emerging roles in plant stress tolerance. OAs are more versatile in their role in plant stress tolerance and are more efficient chelating agents than other acids, such as amino acids. Root OA exudation is important in soil carbon sequestration. These functions are key processes in combating climate change and helping with more sustainable food production. We briefly review the mechanisms behind enhanced biosynthesis, secretion, and regulation of these activities under different stresses, and provide an outline of the transgenic approaches targeted towards the enhanced production and secretion of OAs. A recurring theme of OAs in plant biology is their role as 'acids' modifying pH, as 'chelators' binding metals, or as 'carbon sources' for microbes. We argue that these multiple functions are key factors for understanding these molecules' important roles in plant stress biology. Finally, we discuss how the functions of OAs in plant stress responses could be used, and identify the important unanswered questions.

Soil carbon sequestration by root exudates.

Root exudates are well-known 'labile' sources of soil carbon that can prime microbial activity. Recent investigations suggest that the stability of labile carbon inputs in soil mostly depends upon the physical, chemical, and biological properties of the surroundings. Here, we propose that, in some ecosystems, such as forests and grasslands, root exudates can function as a source of soil organic carbon (SOC) that can be stabilized through various mechanisms leading to long-term sequestration. Increasing soil carbon sequestration is important for capturing atmospheric CO2 and combating climate change issues. Thus, there is an urgent need to preserve existing ecosystems and to adopt strategies such as afforestation, reforestation, and establishment of artificial grasslands to foster carbon sequestration through higher root exudate inputs in the soil.

Microsatellite and mitochondrial DNA analyses unveil the genetic structure of native sheep breeds from three major agro-ecological regions of India.

Sheep farming has been fundamental to many civilizations in the world and is practiced in India since antiquity. Several thousand years of adaptation to local environmental conditions and selective breeding have evolved 44 sheep breeds in India. They are paramount in terms of economic, scientific, and cultural heritage. Genetic characterization information is imperative for sustainable utilization and conservation of ovine heritage. In this study, the genetic diversity, differentiation, and structure of 11 indigenous sheep breeds from three different agro-ecological zones of India were explored with genomic microsatellite loci and mitochondrial DNA (D loop). The estimated diversity parameters indicated that populations retained high levels of genetic diversity (Na = 8.27 ± 0.17; Ho = 0.65 ± 0.01), which provides an optimistic viewpoint for their survival. However, significant inbreeding was also observed in the nine populations. Moderate genetic differentiation existed among the groups (FST = 0.129 ± 0.012), and most likely clusters existing in the dataset are seven. Phylogenetic clustering was in line with the geographical locations of sheep populations. Mitochondrial sequences revealed high haplotype diversity with the existence of maternal haplogroups A, B, and C, and signals of population expansion. Decreased genetic diversity and unique maternal lineage (C) in endangered Tibetan and Bonpala sheep breed, warrant their immediate scientific management. Overall, the quantitative data reported here on the extant variability, and genetic relationships among the Indian sheep breeds, provide critically important inputs that will be valuable for the decision-making process on their management, both for the conservation of endangered breeds, and formulation of breeding programs to check genetic erosion.

Barriers affecting uptake of cervical cancer screening in low and middle income countries: A systematic review.

BACKGROUND: Cervical cancer is the second-most common cancer among women in the developing world and approximately 500,000 cases are diagnosed each year. In developed countries, cervical cancer (CCa) accounts for only 3.6% of newly diagnosed cancers. OBJECTIVE: The present study aims to identify the most effective barriers associated with CCa screening uptake in low and middle-income countries (L and MICs) and aid to adopt effective measures to overcome prevailing barriers to the attainment of CCa uptake in the community. MATERIALS AND METHODS: Health sciences electronic databases like MEDLINE, PubMed, Cochrane library, and Google Scholar were searched for studies published until August 2017. Keywords used for the search were ("cervical cancer screening"), ("barriers"), AND ("low income countries" OR "Middle income countries"). Articles were reviewed and data were extracted by using Mendeley Desktop Software (V-1.17.10). Income-level classification of countries was done as per the World Bank 2017 report. Statistical software like SPSS-V.23 and Medical-V.14 were used for the statistical application. RESULTS: A total of 31 studies met the inclusion criteria with a total of 25,650 participants. The sample size of the included studies ranged from 97 to 5929 participants. Articles majorly reported data on participants from African region (51.6%) and minimally in the Western Pacific region (3.2%). Sampling methods among studies varied from convenience sampling-12 (39.7%) to consecutive sampling-1 (3.2%). Besides, two studies (6.5%) did not discuss their sampling procedures. It was observed that "Lack of information about CCa and its treatment" (Barrier of lack of knowledge and Awareness); "Embracement or shy" (Psychological Barrier); "Lack of time" (structural Barrier); and "Lack of family support" (Sociocultural and religious barrier) were the most commonly reported among all 22 barriers. CONCLUSION: There is a need of policies advancement of CCa screening programs by focusing on aspects of accessibility, affordability, CCa education, and the necessity of screening to improve screening uptake to control the CCa morbidity and mortality rate in L and MIC's.