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Synaptopodin 2-like protein (SYNPO2L) is localized in the sarcomere of cardiomyocytes and is involved in heart morphogenesis. However, the molecular function of SYNPO2L in the heart is not fully understood. We investigated the interaction of SYNPO2L with sarcomeric α-actinin and actin filaments in cultured mouse cardiomyocytes. Immunofluorescence studies showed that SYNPO2L colocalized with α-actinin and actin filaments at the Z-discs of the sarcomere. Recombinant SYNPO2La or SYNPO2Lb caused a bundling of the actin filaments in the absence of α-actinin and enhanced the α-actinin-dependent formation of actin bundles. In addition, high-speed atomic force microscopy revealed that SYNPO2La directly bound to α-actinin via its globular ends. The interaction between α-actinin and SYNPO2La fixed the movements of the two proteins on the actin filaments. These results strongly suggest that SYNPO2L cooperates with α-actinin during actin bundle formation to facilitate sarcomere formation and maintenance. [ABSTRACT FROM AUTHOR]

To elucidate the physiological and genetic mechanisms underlying arsenic (As) absorption and metabolism in rice, we used a set of diverse rice germplasms, called As World Rice Collection (WRC). These cultivars consist of 69 accessions which cover the genetic diversity of almost 32,000 accessions of cultivated rice. The collection was cultivated in a paddy field with naturally abundant level of As. Approximately three times difference at the maximum in grain As concentration was found in WRC. The dominant As species in grains was arsenite, followed by dimethyarsinic acid (DMA) and arsenate, irrespective of cultivars. However, the proportions of As species were different among rice cultivars. These results suggest the possibility that As absorption and metabolim in rice could be genetically controlled.

Cadmium (Cd) concentration in eggplant (Solanum melongena) fruits can be drastically reduced by grafting them with Solanum torvum rootstock. However, mechanisms of Cd uptake in roots and translocation from roots to shoots in both plants are not understood well. We thus characterized symplastic Cd uptake in roots and translocation from roots to shoots via xylem loading process of both plants. Additionally, we also examined effect of other elements in roots uptake and translocation process with the increase of Cd concentration in the medium. Cd concentration in roots of S. torvum was almost similar to that of S. melongena for 7 days. On the other hand, Cd concentrations in the shoots and xylem sap were higher in S. melongena than in S. torvum. A concentration dependent experiment in roots indicated that Km values were almost the same for species, but the Vmax values were 1.5-fold higher in S. melongena than in S. torvum. A concentration dependent experiment in xylem loading process indicated that Km values were approximately 7-fold higher in S. torvum than in S. melongena. These results suggest that xylem loading process is a critical factor for determining Cd accumulation in the shoots of both plants. Several elements concentration in roots and xylem sap of both plants decreased with the increase of Cd concentration in the medium, suggesting that Cd uptake and translocation process are partly mediated by similar transporters involving these elements transport.

We analyzed the real-time translocation of 107Cd from root to shoot among 6 rice cultivars using a positron-emitting tracer imaging system (PETIS). 107Cd first accumulated at the basal region of the shoot within 2 h after the exposure and the signals were much stronger in high-Cd-accumulating cultivars (indica) than in low-Cd-accumulating ones (japonica). 107Cd accumulated increasingly at the upper portion of the shoot with time, and the signals were obviously strong in high-Cd-accumulating cultivars. These results suggest that the different ability of root-to-shoot translocation of Cd is closely related to the genotypic variation in shoot Cd accumulation in rice.

Irgb6 is a priming immune‐related GTPase (IRG) that counteracts Toxoplasma gondii. It is known to be recruited to the low virulent type II T. gondii parasitophorous vacuole (PV), initiating cell‐autonomous immunity. However, the molecular mechanism by which immunity‐related GTPases become inactivated after the parasite infection remains obscure. Here, we found that Thr95 of Irgb6 is prominently phosphorylated in response to low virulent type II T. gondii infection. We observed that a phosphomimetic T95D mutation in Irgb6 impaired its localization to the PV and exhibited reduced GTPase activity in vitro. Structural analysis unveiled an atypical conformation of nucleotide‐free Irgb6‐T95D, resulting from a conformational change in the G‐domain that allosterically modified the PV membrane‐binding interface. In silico docking corroborated the disruption of the physiological membrane binding site. These findings provide novel insights into a T. gondii‐induced allosteric inactivation mechanism of Irgb6. [ABSTRACT FROM AUTHOR]

Decreasing cadmium (Cd) concentrations in rice grains can effectively reduce potential risks to human health because rice is the major contributor to Cd intake in many diets. Among several genes involved in rice Cd accumulation, the loss of function of OsNRAMP5 is known to be effective in reducing grain concentration by inhibiting root uptake. However, disruption of this gene simultaneously decreases manganese (Mn) uptake because OsNRAMP5 is a major Mn transporter. With the aim of improving Mn uptake in OsNRAMP5 mutants while still restricting the grain Cd concentration below the upper limit of international standards, we identified a novel OsNRAMP5 allele encoding a protein in which glutamine (Q) at position 337 was replaced by lysine (K). The mutant carrying the OsNRAMP5-Q337K allele showed intermediate Cd and Mn accumulation between that of the wild-type and OsNRAMP5- knockout lines, and exhibited more resistance to Mn deficiency than the knockout lines. Different amino acid substitutions at position Q337 significantly affected the Cd and Mn transport activity in yeast cells, indicating that it is one of the crucial sites for OsNRAMP5 function. Our results suggest that the OsNRAMP5-Q337K allele might be useful for reducing grain Cd concentrations without causing severe Mn deficiency in rice cultivars through DNA marker-assisted breeding. [ABSTRACT FROM AUTHOR]