Mollusk shell nacre is known for its superior mechanical properties and precisely controlled biomineralization process. However, the question of how mollusks control the morphology of nacre lamellae remains unresolved. Here, a novel 38-kDa extrapallial fluid (EPF) protein, named amorphous calcium carbonate-binding protein (ACCBP), may partially answer this question. Although sequence analysis indicated ACCBP is a member of the acetylcholine-binding protein family, it is actively involved in the shell mineralization process. In vitro, ACCBP can inhibit the growth of calcite and induce the formation of amorphous calcium carbonate. When ACCBP functions were restrained in vivo, the nacre lamellae grew in a screw-dislocation pattern, and low crystallinity CaCO 3 precipitated from the EPF. Crystal binding experiments further revealed that ACCBP could recognize different CaCO 3 crystal phases and crystal faces. With this capacity, ACCBP could modify the morphology of nacre lamellae by inhibiting the growth of undesired aragonite crystal faces and meanwhile maintain the stability of CaCO 3 -supersaturated body fluid by ceasing the nucleation and growth of calcite. Furthermore, the crystal growth inhibition capacity of ACCBP was proved to be directly related to its acetylcholine-binding site. Our results suggest that a "safeguard mechanism" of undesired crystal growth is necessary for shell microstructure formation.

In situ measurements of 14C-CO2 incorporation into 40-[mu]m paradermal leaf sections of sun- and shade-grown spinach leaves were determined. Chlorophyll, carotenoid, and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) content in similar 40-[mu]m paradermal leaf sections was also measured. The carbon fixation gradient did not follow the leaf internal light gradient, which decreases exponentially across the leaf. Instead, the 14C-CO2 fixation was higher in the middle of the leaf. Contrary to expectations, the distribution of carbon fixation across the leaf showed that the spongy mesophyll contributes significantly to the total carbon reduced. Approximately 60% of the carboxylation occurred in the palisade mesophyll and 40% occurred in the spongy mesophyll. Carbon reduction correlated well with Rubisco content, and no correlation between chlorophyll and carotenoid content and Rubisco was observed in sun plants. The correlation among chlorophyll, carotenoids, Rubisco, and carbon fixation was higher in shade leaves than in sun leaves. The results are discussed in relation to leaf photosynthetic and biochemical measurements that generally consider the leaf as a single homogeneous unit.

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Background Exosomes are a type of membrane vesicles secreted by living cells. Recent studies suggest exosome-like nanovesicles (ELNVs) from fruits and vegetables are involved in tissue renewal process and functional regulation against inflammatory diseases or cancers. However, there are few reports on ELNVs derived from medicinal plants. Methods ELNVs derived from Asparagus cochinchinensis (Lour.) Merr. (ACNVs) were isolated and characterized. Cytotoxicity, antiproliferative and apoptosis-inducing capacity of ACNVs against hepatoma carcinoma cell were assessed. The endocytosis mechanism of ACNVs was evaluated on Hep G2 cells in the presence of different endocytosis inhibitors. In vivo distribution of ACNVs was detected in healthy and tumor-bearing mice after scavenger receptors (SRs) blockade. PEG engineering of ACNVs was achieved through optimizing the pharmacokinetic profiles. In vivo antitumor activity and toxicity were evaluated in Hep G2 cell xenograft model. Results ACNVs were isolated and purified using a differential centrifugation method accompanied by sucrose gradient ultracentrifugation. The optimized ACNVs had an average size of about 119 nm and showed a typical cup-shaped nanostructure containing lipids, proteins, and RNAs. ACNVs were found to possess specific antitumor cell proliferation activity associated with an apoptosis-inducing pathway. ACNVs could be internalized into tumor cells mainly via phagocytosis, but they were quickly cleared once entering the blood. Blocking the SRs or PEGylation decoration prolonged the blood circulation time and increased the accumulation of ACNVs in tumor sites. In vivo antitumor results showed that PEGylated ACNVs could significantly inhibit tumor growth without side effects. Conclusion This study provides a promising functional nano platform derived from edible Asparagus cochinchinensis that can be used in antitumor therapy with negligible side effects.

Leaf rolling is receiving considerable attention as an important agronomic trait in rice (Oryza sativa L.). However, little has been known on the molecular mechanism of rice leaf rolling, especially the abaxial rolling. We identified a novel abaxially curled and drooping leaf-dominant mutant from a T₁ transgenic rice line. The abaxially curled leaf phenotypes, co-segregating with the inserted transferred DNA, were caused by overexpression of a zinc finger homeodomain class homeobox transcription factor (OsZHD1). OsZHD1 exhibited a constitutive expression pattern in wild-type plants and accumulated in the developing leaves and panicles. Artificial overexpression of OsZHD1 or its closest homolog OsZHD2 induced the abaxial leaf curling. Histological analysis indicated that both the increased number and the abnormal arrangement of bulliform cells in leaf were responsible for the abaxially curled leaves. We herein reported OsZHD1 with key roles in rice morphogenesis, especially in the modulating of leaf rolling, which provided a novel insight into the molecular mechanism of leaf development in rice.