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No description available.

Pollen development is critical for plant reproduction. Numerous nuclear mutations affect the function of pollen resulting in male sterility. The myb26 mutant is one such male sterile mutant allele, which results in anther indehiscence. Five putative MYB26 interactive proteins were previously identified from screening an Arabidopsis stamen yeast-2-hybrid library with MYB26 as bait. These proteins include Y2H128, Y2H320, Y2560, Y2H620 and Y2H970. Transient expression of these proteins, except Y2H128 were studied in planta by infiltration of Nicotiana benthamiana leaves and all were found to be expressed in the nucleus and co-localised with MYB26. Förster Resonance Energy Transfer (FRET) was used to confirm the positive interaction between MYB26 and the Y2H320 protein. Analysis of the expression and possible function of the putative interactors was examined using SALK knockout T-DNA insertion mutants, RNAi and over-expression lines. SALK knockout lines of four Y2H genes were fully fertile and produced viable pollen despite no expression of the corresponding genes in the insertional mutants of Y2H320 and Y2H560. Independent silencing by RNAi of the other two genes, Y2H970 and Y2H128, also resulted in no alteration in plant phenotype. Transgenic plants over-expressing the Y2H genes also showed no differences in secondary thickening of anthers in endothecium compared to the wild type (Ler). Using a Prom320::GUS transgene, GUS expression was observed in the anthers, nectaries and stigmatic tissues; this pattern of Y2H320 expression corresponds to that seen for MYB26, confirming that interaction in planta is possible. The research also involved an analysis of additional four Arabidopsis male sterile mutants in the M2 and M4 generations. The phenotypes of these mutants were similar to that of the myb26 mutant, where viable pollen was evident, but anther dehiscence did not occur. These novel mutants were not rescued by Jasmonic Acid (JA) treatment. Allelism/complementation analyses indicated that the two mutants c20 and mss are alleles of myb26, whilst msak and c12 are novel mutations at different loci. Gene mapping of the MSAK gene indicated that it is located on chromosome 1. Further higher resolution genetic mapping with Simple Sequence Length Polymorphism (SSLP) molecular markers identified a closer linked marker (12.57 cM to MSAK), suggesting that the gene is located ~3.2 Mb from the start of chromosome 1. A possible candidate for MSAK gene located within the region 3.4-3.5 Mb is the transcription factor Transducin/WD40 repeat-like protein (At1g10580; located at 3.49 Mb), which is involved in pollen development. Further investigation of additional candidate genes for MSAK in the region of ~3.0-4.0 Mb of chromosome 1 that are related to male gametophyte, pollen development or belong to MYB superfamily identified a number of genes, one likely candidate is At1g10770 (located at ~3.59 Mb). Previous reports indicated that reduction of At1g10770 transcript resulted in pollen tube growth retardation, partial male sterility and reduced seed set.

Sauropus androgynus, commonly known as ‘sweet shoot’ is an underutilized crop known for its high nutritive values and medicinal properties. To date, scientific studies assessing the potentially important benefits of sweet shoot for use as medicinal plants are still limited, with only six studies reporting on in vitro propagation and nine articles describing the production of secondary metabolites. The present study revealed that shadehouse-grown plants contained a low yield of bioactive phytochemicals, such as phenolic (61.20 µg/10g FW), flavonoid (193.62 µg/10g FW), naringenin (128.01 µg/10g FW), quercetin (1.56 µg/10g FW) and kaempferol (274.85 µg/10g FW). Moreover, it also had very low antioxidant activity in DPPH (54.03%) and FRAP (397.56 µg/10g FW) assay. The elicitation of cultured tissues is therefore necessary to improve the production of phytochemical compounds and to increase the antioxidant capacity in sweet shoot. In this study, four different types of cultured tissues (in vitro shoot cultures, light-induced callus, dark-induced callus and somatic embryos) were selected to achieve this goal, followed by the extraction of phytochemicals from these cultured tissues treated with elicitors and precursor for better production of phytochemicals. For in vitro shoot induction, nodal explants cultured on semi-solid MS medium supplemented with 2.0 mg/l 6-benzylaminopurine (BAP) and 0.5 mg/l indole-3-acetic acid (IAA) produced the highest number of shoots (7 shoots per explant) with longer shoot length (5.74 cm). For light-induced callus induction, leaf explants grown in illuminated conditions with semi-solid MS medium enriched with 2.0 mg/l α-naphthalene acetic acid (NAA) and 1.0 mg/l kinetin showed good proliferation from the leaf explants (71.67%) with the highest callus fresh weight (4.53 g) and highest callus expansion rate (18.50 cm2). Likewise, leaf explants induced in dark condition on semi-solid MS medium containing similar hormone composition, also displayed the highest callus fresh weight of 4.54 g and callus expansion rate of 13.85 cm2. Three-month-old dark-induced callus were transferred onto liquid MS medium fortified with a different concentration of NAA and kinetin to further induce somatic embryos. After three weeks of callus inoculation, as high as 83.33% of embryogenic cell cultures achieved its maximum density of 5.2 ml in liquid MS medium supplemented with 2.0 mg/l NAA and 1.0 mg/l kinetin. In histodifferentiation medium (liquid MS medium containing 1.0 mg/l NAA and 0.5 mg/l kinetin), a mean number of 15.60, 14.80 and 13.20 embryos per g callus of globular, heart-shaped and torpedo-shaped embryos developed respectively after 9 weeks of embryo induction. The torpedo-shaped embryos were then inoculated into hormone-free MS medium and 90% of these embryos successfully differentiated into cotyledonary embryos after 3 weeks of maturation. These results showed a complete ontogeny of sweet shoot somatic embryo from the globular stage to heart-shaped, torpedo-shaped and cotyledonary stage. After two months of shoot initiation on MS medium supplemented with 2.0 mg/l BAP and 0.5 mg/l IAA, a relatively high percentage (>75%) of shoot proliferation occurred from nodal derived shoot (6.74 shoots per explant), light-induced callus (6.23 shoots per callus) and somatic embryos (6.45 shoots per embryo) of sweet shoot. These well proliferated shoots were then subjected to root initiation in half strength MS medium containing 1.0 mg/l IAA and high percentage of root formation was successfully achieved in 90% of the plantlets after 10 days of culture. For hardening off, the rooted plantlets were transferred to culture jars containing purified water and maintained at ambient conditions for one month. High survival rate (>76.67%) was achieved in perlite:compost mixture (1:1) after one month of acclimatization in shadehouse. To enhance the production of phytochemicals and antioxidant capacity in tissue cultures of sweet shoot, elicitor and precursor treatments served as alternative methods in influencing the biosynthetic pathway for the accumulation of phytochemicals. In this study, shadehouse-grown plants and cultured tissues of sweet shoot were treated individually with different concentrations of methyl jasmonate (MJ), salicylic acid (SA) and phenylalanine (Phe) for a treatment period of 3 weeks. Light-induced callus culture produced the highest amount of phenolic and flavonoid compounds amongst the tested plant samples with those treated with Phe producing the highest antioxidants, followed by MJ and SA. After 3 weeks of Phe treatment at 20 mg/l, the highest levels of total phenolic (246.62 µg/10g FW), total flavonoid (636.26 µg/10g FW), naringenin (12081.05 µg/10g FW), quercetin (134.36 µg/10g FW), kaempferol (11325.13 µg/10g FW) and antioxidant activities (97.35% for DPPH and 5941.66 µg/10g FW for FRAP assay) were detected in light-induced callus cultures of sweet shoot. Since phenylalanine ammonia-lyase (PAL) and chalcone synthase (CHS) were the key enzymes for the biosynthesis of phenolics and flavonoids, both enzymatic activities were also measured in light-induced callus cultures treated with Phe. The highest PAL (101.18 mmol CA/g FW) and CHS (14.49 nkat/mg protein) enzymatic activities were also attained in light-induced callus cultures fed with 20 mg/l of Phe at week 3. Light-induced callus cultures treated with Phe produced the highest amounts of phytochemicals, antioxidant capacity and enzymatic activities, and these results were chosen to undergo Pearson’s correlation coefficient analysis, which verified the positive co-relationship seen between all of the above-mentioned parameters. These findings showed that the addition of Phe enhanced the enzymatic activities in the phenylpropanoid pathway and increased the concentrations of phenolic and flavonoid compounds (naringenin, quercetin, kaempferol) which in turn contributed to the increase in antioxidant activities in light-induced callus cultures of sweet shoot. Data from this study showed that sweet shoot has the potential to be developed as a plant-based antioxidant for the pharmaceutical industry. Additionally, this study is the first to report on the complete ontogeny of sweet shoot and the positive effects of elicitation in tissue cultures of sweet shoot.

In this study, theoretical and experimental approaches were combined, using Arabidopsis as the studied species. The multi-scale model incorporates the following, existing sub-models: a phenology model that can predict the flowering time of plants grown in the field, a gene circuit of the circadian clock network that regulates flowering through the photoperiod pathway, a process-based model describing carbon assimilation and resource partitioning, and a functional-structural module that determines shoot structure for light interception and root growth. First, the phenology model was examined on its ability to predict the flowering time of field plantings at different sites and seasons in light of the specific meteorological conditions that pertained. This analysis suggested that the synchrony of temperature and light cycles is important in promoting floral initiation. New features were incorporated into the phenology model that improved its predictive accuracy across seasons. Using both lab and field data, this study has revealed an important seasonal effect of night temperatures on flowering time. Further model adjustments to describe phytochrome (phy) mutants supported the findings and implicated phyB in the temporal gating of temperature-induced flowering. The improved phenology model was next linked to the clock gene circuit model. Simulation of clock mutants with different free-running periods highlighted the complex mechanism associated with daylength responses for the induction of flowering. Finally, the carbon assimilation and functional-structural growth modules were integrated to form the multi-component, whole-plant model. The integrated model was successfully validated with experimental data from a few genotypes grown in the laboratory. In conclusion, the model has the ability to predict the flowering time, leaf biomass and ecosystem exchange of plants grown under conditions of varying light intensity, temperature, CO2 level and photoperiod, though extensions of some model components to incorporate more biological details would be relevant. Nevertheless, this meso-scale model creates obvious application routes from molecular and cellular biology to crop improvement and biosphere management. It could provide a framework for whole-organism modelling to help address global issues such as food security and the energy crisis.