No abstract

Plants can obtain superinduction of defense against unpredictable challenges based on prior acclimation, but the mechanisms involved in the acclimation memory are little known. The objective of this study was to characterize mechanisms of heat acclimation memory in Rhododendron hainanense, a thermotolerant wild species of azalea. Pretreatment of a 2-d recovery (25/18°C, day/night) after heat acclimation (37°C, 1 h) (AR-pt) did not weaken but enhanced acquired thermotolerance in R. hainanense with less damaged phenotype, net photosynthetic rate, and membrane stability than non-acclimation pretreated (NA-pt) plants. Combined transcriptome and proteome analysis revealed that a lot of heat-responsive genes still maintained high protein abundance rather than transcript level after the 2-d recovery. Photosynthesis-related genes were highly enriched and most decreased under heat stress (HS: 42°C, 1 h) with a less degree in AR-pt plants compared to NA-pt. Sustainably accumulated chloroplast-localized heat shock proteins (HSPs), Rubisco activase 1 (RCA1), beta-subunit of chaperonin-60 (CPN60b), and plastid transcriptionally active chromosome 5 (pTAC5) in the recovery period probably provided equipped protection of AR-pt plants against the subsequent HS, with less damaged photochemical efficiency and chloroplast structure. In addition, significant higher levels of RCA1 transcripts in AR-pt compared to NA-pt plants in early stage of HS showed a more important role of RCA1 than other chaperonins in heat acclimation memory. The novel heat-induced RCA1, rather than constitutively expressed RCA2 and RCA3, showed excellent thermostability after long-term HS (LHS: 42/35°C, 7 d) and maintained balanced Rubisco activation state in photosynthetic acclimation. This study provides new insights into plant heat acclimation memory and indicates candidate genes for genetic modification and molecular breeding in thermotolerance improvement.

No abstract

Auxins and humic acid (HA) were investigated for their roles in adventitious root induction in azalea microshoots in our previous study. To reveal the regulatory mechanisms of auxins and HA in this process, measurements of the levels of reactive oxygen species (ROS), carbohydrates, and phenolic compounds and gene expression during in vitro root development were performed. During the adventitious root induction process, ROS levels in shoots treated with auxins and HA increased compared to untreated shoots, especially during the earliest period after transfer to the media. Media supplemented with NAA experienced increases in H2O2 contents by 480%and 250%, respectively, after 7 and 14 days of culture. The phenolic compound levels were also enhanced in the shoots treated with auxins and HA, reflecting the different rooting-promoting abilities of both auxins and HA. The highest levels of total phenolic [68.6 mg·g−1 fresh weight (FW)], polyphenolic acids (121.72 μg caffic acid/g FW), and total flavonols (162.42 μg quercetin/g FW) were recorded after 21 days for NAA media, but the maximum levels of anthocyanins (49.76 μg cyanindin/g FW) were recorded after 21 days for IBA medium. Soluble carbohydrate, starch, and soluble protein levels were increased in the shoots treated with all treatments; however, the influence of NAA treatments was stronger than that of other treatments for most investigated parameters. The NAA significantly enhanced soluble carbohydrates by 30%, 37%, and 25%, respectively, at 14, 21, and 28 days compared with untreated microshoots. Expression of the POD1 gene increased in the shoots submitted to HA treatment media. Expression levels of auxin response factors (ARFs) increased with IBA- and NAA-treated explants, suggesting that ARFs may have diverse regulatory roles in adventitious root induction in evergreen azalea. Moreover, the profiles of the IAA1, IAA9, IAA14, and IAA27 transcripts were analyzed to reveal their roles in the adventitious rooting of evergreen azalea microshoots. These results indicate that auxins and HA promote adventitious root induction in Rhododendron plants through their impact on ROS, carbohydrate contents, phenolic compound levels, and expression levels of different genes related to root development in evergreen azalea plants.

Two crude heteropolysaccharides were isolated from fruits of Caryota mitis and Chamaerops humilis in percentages of 2.65 and 3.89, respectively. In the case of Caryota mitis (CM) polysaccharide, it consisted of galactose, glucose and mannose as the predominant monosaccharides. While mannose, galactose and arabinose were respectively the predominant monosaccharides in the structure of Chamaerops humilis (CH) crude polysaccharide. Sixteen common amino acids were recognized to be components of the protein-bound polysaccharides of CM and CH. The major amino acid in CM and CH polysaccharides was tyrosine (1.091ng/g) and arginine (0.684 ng/g), respectively. Antioxidant activities of tested polysaccharides were examined by measuring its scavenging ability on 2,2-diphenyl-1-picrylhydrazyl and ferric reducing activity power assay. In a concentration of 1 mg/ml, CM and CH polysaccharides recorded FRAP values of 0.56 and 0.44 µmol Fe ++ /g, respectively. The scavenging activity of CM sample was higher (IC 50 , 422.11 µg/ml) than that of CH polysaccharide (IC 50 , 630.0 µg/ml). Also, the antitumor activity of CM and CH polysaccharides was investigated using HepG2 and MCF-7 human cell lines. The polysaccharide of Caryota mitis had a higher antitumor activity than that of CHPs; it had IC 50 values of 13.6 and 46.4 µg/ml in HepG2 and MCF-7 assays, respectively.

No abstract

The present investigation was carried out to study the direct and indirect micropropagation of Antirrhinum majus In order to reduce the cost of production and to ensure the production of genetically identical ornamental plantlets for further field culture as well as for medium-term conservation for future use and research. For the direct micropropagation addition of 70.0 % Ethyl alcohol for 30 sec and 30.0% commercial Clorox (1.30% NaOCl) for 5.00 minute were the best treatment for seeds sterilization. Hypocotyl, cotyledon and cotyledonary node were excised from in vitro grown seedlings. These explants were cultured for adventitious shoot regeneration. Using MS medium supplemented with BAP at 0.50 and 1.00 mg/L produced the highest shoots number of 13.50 shoots for both of them. Microshoots were rooted on MS medium containing IBA, IAA or NAA at 0.0, 0.50, 1.00 or 2.00 mg/L. Ninety percent of the microshoots were rooted on MS medium supplemented with 0.50 and 1.0 mg/L IBA. The rooting which achieved on medium fortified with NAA at 0.50 mg/L significantly recorded the highest roots number of 12.83 roots. A total of 90% survival was achieved and an increase in shoots length (12.71cm) when rooted explants were acclimatized ex vitro using 1: 1 soil: vermiculite mixture. On the other hand, for indirect micropropagation, explants successfully formed callus by using MS medium supplemented with TDZ at