Bioprinting technology shows potential in tissue engineering for the fabrication of scaffolds, cells, tissues and organs reproducibly and with high accuracy. Bioprinting technologies are mainly ...divided into three categories, inkjet-based bioprinting, pressure-assisted bioprinting and laser-assisted bioprinting, based on their underlying printing principles. These various printing technologies have their advantages and limitations. Bioprinting utilizes biomaterials, cells or cell factors as a "bioink" to fabricate prospective tissue structures. Biomaterial parameters such as biocompatibility, cell viability and the cellular microenvironment strongly influence the printed product. Various printing technologies have been investigated, and great progress has been made in printing various types of tissue, including vasculature, heart, bone, cartilage, skin and liver. This review introduces basic principles and key aspects of some frequently used printing technologies. We focus on recent advances in three-dimensional printing applications, current challenges and future directions.
Cell adhesion has tremendous impact on the function of culture platforms and implants. Cell-adhesive proteins and peptides have been extensively used for decades to promote cell adhesion, however, ...their application suffers from their easy enzymatic degradation, difficulty in large-scale preparation and expensiveness. To develop the next-generation cell-adhesive materials, we mimic the cell adhesion functions and mechanisms of RGD and KRSR peptides and design cell-adhesive cationic-hydrophobic amphiphilic β-amino acid polymers that are stable upon proteolysis and easily prepared in large scale at low cost. The optimal polymer strongly promotes cell adhesion, using preosteoblast cell as a model, by following dual mechanisms that are independent of sequence and chirality of the statistic copolymer. Our strategy opens avenues in designing the next-generation cell-adhesive materials and may guide future studies and applications.
In male reproductive development in plants, meristemoid precursor cells possessing transient, stem cell-like features undergo cell divisions and differentiation to produce the anther, the male ...reproductive organ. The anther contains centrally positioned microsporocytes surrounded by four distinct layers of wall: the epidermis, endothecium, middle layer, and tapetum. Here, we report that the rice (Oryza sativa) basic helix-loop-helix (bHLH) protein TDR INTERACTING PROTEIN2 (TIP2) functions as a crucial switch in the meristemoid transition and differentiation during early anther development. The tip2 mutants display undifferentiated inner three anther wall layers and abort tapetai programmed cell death, causing complete male sterility. TIP2 has two paralogs in rice, TDR and EAT1, which are key regulators of tapetai programmed cell death. We revealed that TIP2 acts upstream of TDR and EAT1 and directly regulates the expression of TDR and EAT1. In addition, TIP2 can interact with TDR, indicating a role of TIP2 in later anther development. Our findings suggest that the bHLH proteins TIP2, TDR, and EAT1 play a central role in regulating differentiation, morphogenesis, and degradation of anther somatic cell layers, highlighting the role of paralogous bHLH proteins in regulating distinct steps of plant cell-type determination.
Anther cuticle and pollen exine act as protective envelopes for the male gametophyte or pollen grain, but the mechanism underlying the synthesis of these lipidic polymers remains unclear. Previously, ...a tapetum‐expressed CYP703A3, a putative cytochrome P450 fatty acid hydroxylase, was shown to be essential for male fertility in rice (Oryza sativa L.). However, the biochemical and biological roles of CYP703A3 has not been characterized. Here, we observed that cyp703a3‐2 caused by one base insertion in CYP703A3 displays defective pollen exine and anther epicuticular layer, which differs from Arabidopsis cyp703a2 in which only defective pollen exine occurs. Consistently, chemical composition assay showed that levels of cutin monomers and wax components were dramatically reduced in cyp703a3‐2 anthers. Unlike the wide range of substrates of Arabidopsis CYP703A2, CYP703A3 functions as an in‐chain hydroxylase only for a specific substrate, lauric acid, preferably generating 7‐hydroxylated lauric acid. Moreover, chromatin immunoprecipitation and expression analyses revealed that the expression of CYP703A3 is directly regulated by Tapetum Degeneration Retardation, a known regulator of tapetum PCD and pollen exine formation. Collectively, our results suggest that CYP703A3 represents a conserved and diversified biochemical pathway for in‐chain hydroxylation of lauric acid required for the development of male organ in higher plants.
Transport of photoassimilates from leaf tissues (source regions) to the sink organs is essential for plant development. Here, we show that a phytohormone, the brassinosteroids (BRs) promotes pollen ...and seed development in rice by directly promoting expression of Carbon Starved Anther (CSA) which encodes a MYB domain protein. Over‐expression of the BR‐synthesis gene D11 or a BR‐signaling factor OsBZR1 results in higher sugar accumulation in developing anthers and seeds, as well as higher grain yield compared with control non‐transgenic plants. Conversely, knockdown of D11 or OsBZR1 expression causes defective pollen maturation and reduced seed size and weight, with less accumulation of starch in comparison with the control. Mechanically, OsBZR1 directly promotes CSA expression and CSA directly triggers expression of sugar partitioning and metabolic genes during pollen and seed development. These findings provide insight into how BRs enhance plant reproduction and grain yield in an important agricultural crop.
The timely programmed cell death (PCD) of the tapetum, the innermost somatic anther cell layer in flowering plants, is critical for pollen development, including the deposition and patterning of the ...pollen wall. Although several genes involved in tapetal PCD and pollen wall development have been characterized, the underlying regulatory mechanism remains elusive. Here we report that
(
), which encodes an AT-hook nuclear localized protein in rice (
), is required for normal tapetal PCD and pollen wall development. The mutant
showed persistent tapetal cells and abnormal pollen wall patterning including absent nexine, collapsed bacula, and disordered tectum. The defective tapetal PCD phenotype of
was similar to that of a PCD delayed mutant,
, in rice, while the abnormal pollen wall patterning resembled that of a pollen wall defective mutant,
, in Arabidopsis (
). Levels of anther cutin monomers in
anthers were significantly reduced, as was expression of a series of lipid biosynthetic genes. PTC2 transcript and protein were shown to be present in the anther after meiosis, consistent with the observed phenotype. Based on these data, we propose a model explaining how PTC2 affects anther and pollen development. The characterization of PTC2 in tapetal PCD and pollen wall patterning expands our understanding of the regulatory network of male reproductive development in rice and will aid future breeding approaches.
Rice is one of the most important crops as it supports over25%of total caloric intake for humans（Kusano et al.,2015）.The world population reached 7.3 billion in 2015 and is projected to reach 8.5 ...billion in 2030（Word Population Prospects：2015 Revision）.
Plant Rho small GTPases (Rop/Rac) are versatile molecular switches regulating many plant developmental processes. Particularly, their important functions in regulating pollen development have been ...demonstrated in Arabidopsis. A group of conserved Rop/Rac activators RopGEFs were recently reported to regulate rice (Oryza sativa) pollen tube germination, indicating that rice and Arabidopsis may have a conserved Rop/Rac mediated signaling pathway in regulating pollen tube growth. However, the Rop/Rac activated by the rice pollen specific RopGEFs remains to be identified. Here we demonstrated a Rop/Rac gene, OsRacB, co‐expressed with the mature pollen expressed OsRopGEF2/3/6/8. The knockout mutants were normal in anther and pollen development but defective in the pollen grain germination, suggesting a specific and non‐redundant role of OsRacB in the mature pollen. We further demonstrated that OsRacB is directly activated by the pollen specific expressing OsRopGEFs in vitro. Together with the previous study, we establish a RopGEF‐Rop/Rac regulon which plays essential roles in rice pollen grain germination. Our data encourage further identification of the upstream and downstream players of RopGEF‐Rop/Rac signaling in pollen germination and have agricultural implications for breeding robust seed yielding cultivars.
Plant specific small Rho GTPases have been shown as important molecular switches in many processes. We demonstrate that the rice Rho small GTPase OsRacB interacts with a group of pollen preferentially expressed RopGEFs to regulates pollen germination.
Jasmonates (JAs) are crucial to the coordination of plant stress responses and development. JA signaling depends on JASMONATE-ZIM DOMAIN (JAZ) proteins that are destroyed by the SCF
-mediated 26S ...proteasome when the JAZ co-receptor COI1 binds active JA or the JA-mimicking phytotoxin coronatine (COR). JAZ degradation releases JAZ-interacting transcription factors that can execute stress and growth responses. The JAZ proteins typically contain Jas motifs that undergo conformational changes during JA signal transduction and that are important for the JAZ-COI1 interaction and JAZ protein degradation. However, how alterations in the Jas motif and, in particular, the JAZ degron part of the motif, influence protein stability and plant development have not been well explored. To clarify this issue, we performed bioassays and genetic experiments to uncover the function of the OsJAZ1 degron in rice JA signaling. We found that substitution or deletion of core segments of the degron altered the OsJAZ1-OsCOI1b interaction in a COR-dependent manner. We show that these altered interactions function as a regulator for JA signaling during flower and root development. Our study therefore expands our understanding of how the JAZ degron functions, and provides the means to change the sensitivity and specificity of JA signaling in rice.
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