Recent Progresses in Eco-Friendly Fabrication and Applications of Sustainable Aerogels from Various Waste Materials.

Tons of waste from residential, commercial and manufacturing activities are generated due to the growing population, urbanization and economic development, prompting the need for sustainable measures. Numerous ways of converting waste to aerogels, a novel class of ultra-light and ultra-porous materials, have been researched to tackle the issues of waste. This review provides an overview of the status of aerogels made from agricultural waste, municipal solid, and industrial waste focusing on the fabrication, properties, and applications of such aerogels. The review first introduced common methods to synthesize the aerogels from waste, including dispersion and drying techniques. Following that, numerous works related to aerogels from waste are summarized and compared, mainly focusing on the sustainability aspect of the processes involved and their contributions for environmental applications such as thermal insulation and oil absorption. Next, advantages, and disadvantages of the current approaches are analyzed. Finally, some prospective waste aerogels and its applications are proposed.

Induction of in vitro flowering in Dendrobium Madame Thong-In (Orchidaceae) seedlings is associated with increase in endogenous N(6)-(Delta (2)-isopentenyl)-adenine (iP) and N (6)-(Delta (2)-isopentenyl)-adenosine (iPA) levels.

We analysed the endogenous cytokinin levels of Dendrobium Madame Thong-In seedlings grown in vitro during vegetative and flowering-inductive periods. HPLC was used to fractionate the extracts and radioimmunoassay (RIA) was used for assay of zeatin (Z), dihydrozeatin (DZ), N(6)-(Delta(2)-isopentenyl)-adenine (iP) and their derivatives. Coconut water used in experiments was found to contain high level (>136 pmol ml(-1)) of zeatin riboside (ZR). Protocorms and seedlings cultured in medium with coconut water were found to contain 0.5-3.9 pmol g(-1) FW of the cytokinins analysed. Seedlings (1.0-1.5 cm) cultured in flowering-inductive liquid medium containing 6-benzyladenine (BA, 4.4 muM) and coconut water (CW, 15%) contained up to 200 and 133 pmol g(-1) FW of iP and iPA, respectively. These levels were significantly higher than all other cytokinins analysed in seedlings of the same stage and were about 80- to 150-folds higher than seedlings cultured in non-inductive medium. During the transitional (vegetative to reproductive) stage, the endogenous levels of iP (178 pmol g(-1) FW) and iPA (63 pmol g(-1) FW) were also significantly higher than cytokinins in the zeatine (Z) and dihydrozeatin (DZ) families in the same seedlings. Seedlings that grew on inductive medium but remained vegetative contained lower levels of iPA. The importance of the profiles of iP and its derivatives in induction of in vitro flowering of D. Madame Thong-In is discussed.

High frequency early in vitro flowering of Dendrobium Madame Thong-In (Orchidaceae).

We have successfully developed a method to induce early in vitro flowering of the self-pollinated seedlings of a tropical orchid hybrid, Dendrobium Madame Thong-In. Transition of vegetative shoot apical meristem to inflorescence meristem was observed when young protocorms were cultured in modified KC liquid medium. In contrast, protocorms cultured on Gelrite-solidified medium only produced axillary shoots and roots. CW was required to trigger the transitional shoot apical meristem and BA enhanced inflorescence stalk initiation and flower bud formation. However, normal flower development was deformed in liquid medium but developed fully upon transferring to two-layered (liquid over Gelrite-solidified) medium. Under optimal condition, in vitro flowering was observed about 5 months after seed sowing. Segregation of flower colours was observed in these seedlings and seedpods formed upon artificial pollination of the in vitro flowers.

Investigation of cytokinin-deficient phenotypes in Arabidopsis by ectopic expression of orchid DSCKX1.

The plant hormone cytokinin plays a major role in regulating plant growth and development. Here we generated cytokinin-reduction Arabidopsis plants by overexpressing a heterologous cytokinin oxidase gene DSCKX1 from Dendrobium orchid. These transgenic plants exhibited reduced biomass, rapid root growth, decreased ability to form roots in vitro, and reduced response to cytokinin in growing calli and roots. Furthermore, the expression of KNAT1, STM, and CycD3 genes was significantly reduced in the transgenic plants, suggesting that cytokinin may function to control the cell cycles and shoot/root development via regulation of these genes.

Functional characterisation of a cytokinin oxidase gene DSCKX1 in Dendrobium orchid.

Cytokinin oxidase plays an important role in the cytokinin regulatory processes. We have cloned a novel putative cytokinin oxidase, DSCKX1 (Dendrobium Sonia cytokinin oxidase), by mRNA differential display from shoot apices of Dendrobium Sonia cultured in the presence of BA. The DSCKX1 gene appears to have three alternative splicing forms and its expression of DSCKX1 was induced in a tissue-specific manner by cytokinins. In transgenic orchid plants overexpressing DSCKX1, the elevated level of cytokinin oxidase activity was accompanied by a reduction of cytokinin content. These plants exhibited slow shoot growth with numerous and long roots in vitro. Their calli also showed decreased capability of shoot formation. Conversly, antisense transgenic plants showed rapid proliferation of shoots and inhibition of root growth combined with a higher endogenous cytokinin content than wild-type plants. Thus DSCKX1 appears to play an important role on cytokinin metabolism and the related developmental programmes in orchid.

Isolation and characterization of the orchid cytokinin oxidase DSCKX1 promoter.

The orchid DSCKX1 is a new member of the cytokinin oxidase gene family, which catalyses the degradation of cytokinins bearing unsaturated isoprenoid side chains. A 3.7 kb fragment upstream of the DSCKX1 coding region was isolated, sequenced and characterized by deletion analysis of DSCKX1::beta-glucuronidase gene fusions using transient orchid and stable Arabidopsis transformation systems. Functional analysis of 5' deletions defined the 5'-upstream region that directs the expression in distinct tissues. Regulatory elements affecting the cytokinin induction of the DSCKX1 gene have also been delineated

Spatial and temporal expression of the orchid floral homeotic gene DOMADS1 is mediated by its upstream regulatory regions.

The orchid floral homeotic gene, DOMADSI, is a marker gene specifically expressed in the transitional shoot apical meristem during floral transition in Dendrobium Madame Thong-In. DOMADSI is not detectable in vegetative tissues except a weak expression in the stem. Its transcript is uniformly localized in both of the inflorescence meristem and floral primordia, and later expressed in almost all of the floral organs. We isolated and sequenced a 3.5 kb DOMADSI promoter fragment upstream of the transcription start site, demonstrating the location of several putative DNA-binding sites, through which MADS-box and class I knox genes may modulate the DOMADSI expression. To gain insight into the molecular basis of the regulation of DOMADS1, deletion analysis of the DOMADSI::beta-glucuronidase (GUS) gene fusions was performed by means of the stable orchid transformation systems. The study shows that the full-length upstream promoter sequence confers the same spatial and temporal GUS staining pattern as that of the distribution of DOMADSI RNA during orchid development. We also identified the distinct cis-acting regulatory regions required for the control of DOMADS1 expression in vegetative and reproductive tissues, as well as the shoot apical meristem during floral transition.

Differential expression and characterization of three metallothionein-like genes in Cavendish banana (Musa acuminata).

Metallothioneins (MTs) are cysteine-rich polypeptides that are involved in metal detoxification and homeostasis in both prokaryotes and eukaryotes. In this study, we report the isolation and characterization of three members (MT2A, MT2B and MT3) of the MT-like gene family from ripening banana fruit and their differential expression in various banana organs and during fruit development and ripening. All members of the MT-like gene encode small cysteine-rich polypeptides of 65-79 amino acid residues. MT2A shared a high sequence similarity (54-77%) with several type-2 MTs in plants, while MT3 was highly homologous (51-61%) with type-3 MTs. The three members expressed differentially in various organs but transcripts were generally more abundant in reproductive than vegetative organs. During fruit development, the MT2A transcript was barely detectable in ovary but increased to a high level in young fruit at 20 days after shooting (DAS) and declined gradually thereafter as fruit developed. In contrast, both MT2B and MT3 expressed poorly in young fruits (20-60 DAS) and transcripts were detected only in fruits at later stages of development. As ripening progressed, expression of MT2A decreased but that of MT3 increased. Expression of MT members during ripening appeared to be differentially regulated by ethylene, whose levels were low in FG and TY fruit but surged climacteristically in MG and declined sharply as ripening advanced further. Exogenous application of ethylene at 5 ppm or higher concentrations down-regulated MT2A expression and the inhibitory effect of ethylene could be partially suppressed by the presence of norbornadiene, an inhibitor of ethylene action. Ethylene had no effect on transcript accumulation of MT2B and MT3. However, MT3 expression was greatly enhanced in response to metals such as CdSO4, CuSO4 and ZnSO4. These results suggest that increased MT3 expression may be associated with excess metal ions present in ripening fruit tissues. This study also provided evidence, for the first time, that ethylene and metals play a regulatory role in expression of MT-like genes in banana.