https://ogma.newcastle.edu.au/vital/access/ /manager/Index ${session.getAttribute("locale")} 5 https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:44997 trans-acting small-interfering RNA (tasiRNA) production allowed for use of the loss-of-function mutant lines, drb1, drb2, drb4, and ago7, to further functionally characterize the TAS3 pathway in Arabidopsis thaliana (Arabidopsis). Towards achieving this goal, we also describe the developmental and molecular phenotypes expressed by three newly generated Arabidopsis lines, the drb1ago7, drb2ago7, and drb4ago7 double mutants. We show that the previously reported developmental abnormalities displayed by the drb1, drb2, drb4, and ago7 single mutants, are further exacerbated in the drb1ago7, drb2ago7, and drb4ago7 double mutants, with rosette area, silique length, and seed set all impaired to a greater degree in the double mutants. Molecular assessment of the TAS3 pathway in the floral tissues of the seven analyzed mutants revealed that DRB1 is the sole DRB required for miR390 sRNA production. However, DRB2 and DRB4 appear to play secondary roles at this stage of the TAS3 pathway to ensure that miR390 sRNA levels are tightly maintained. We further show that the expression of the TAS3-derived tasiARF target genes, AUXIN RESPONSE FACTOR2 (ARF2), ARF3, and ARF4, was altered in drb1ago7, drb2ago7, and drb4ago7 flowers. Altered ARF2, ARF3, and ARF4 expression was in turn demonstrated to lead to changes in the level of expression of KAN1, KAN3, and KAN4, three KANADI transcription factor genes known to be transcriptionally regulated by ARF2, ARF3, and ARF4. Taken together, the demonstrated relationship between altered ARF and KAN gene expression in drb1ago7, drb2ago7 and drb4ago7 flowers, could, in part, explain the more severe developmental defects displayed by the double mutants, compared to milder impact that loss of only a single piece of TAS3 pathway protein machinery was demonstrated to have on drb1, drb2, drb4 and ago7 reproductive development.]]> Wed 26 Oct 2022 09:28:43 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:48593 Wed 22 Mar 2023 08:46:40 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:38723 Wed 19 Jan 2022 10:04:17 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:33810 ShSUT1 in sucrose mobilisation and storage in sugarcane was investigated by employing RNAi technology to reduce the expression of this gene. Transcript profiling in non-transformed plants showed an alignment between expression and sucrose concentration, with strongest expression in source leaves and increasing expression through the daylight period of a diurnal cycle. Five transgenic plant lines were produced with reduced ShSUT1 expression ranging from 52 to 92% lower than control plants. Differential suppression of ShSUT1 sequence variants in the highly polyploid sugarcane genome were also investigated. Amplicon sequencing of the ShSUT1 variants within the transgenic lines and controls showed no preferential suppression with only minor differences in the proportional expression of the variants. A range of altered sugar, fibre and moisture contents were measured in mature leaf and internode samples, but no phenotype was consistently exhibited by all five transgenic lines. Phenotypes observed indicate that ShSUT1 does not play a direct role in phloem loading. ShSUT1 is likely involved with retrieving sucrose from intercellular spaces for transport and storage.]]> Wed 16 Jan 2019 14:37:48 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:26867 Wed 11 Apr 2018 17:04:35 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:19866 Wed 11 Apr 2018 15:06:19 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:19754 Wed 11 Apr 2018 14:07:53 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:29329 Wed 11 Apr 2018 13:14:56 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:23091 Wed 11 Apr 2018 11:37:20 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:14798 Wed 11 Apr 2018 10:49:42 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:50712 Wed 02 Aug 2023 15:42:45 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:54514 Tue 27 Feb 2024 15:47:21 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:47077 Tue 13 Dec 2022 16:21:31 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:49855 Tue 06 Jun 2023 15:03:36 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:33603 Tue 03 Sep 2019 17:58:42 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:51304 Thu 31 Aug 2023 14:21:03 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:43784 Thu 29 Sep 2022 14:15:59 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:45368 Thu 27 Oct 2022 15:02:22 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:42559 Thu 25 Aug 2022 11:05:11 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:33601 In planta studies of phloem unloading encounter substantial technical challenges in accessing phloem within a meshwork of vascular/ground tissues. Thus, current understanding of phloem-unloading mechanisms largely has been deduced from indirect experimental measures or modelling. Here we highlight recent advances in understanding phloem unloading mechanisms and identify where important knowledge gaps remain.]]> Thu 22 Nov 2018 16:43:25 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:33602 Sorghum bicolor SUTs SbSUT1 and SbSUT5 were characterized by determining their transport properties heterologously expressed in yeast or Xenopus laevis oocytes, and their in planta cellular and subcellular localization. The plasma membrane-localized SbSUT1 and SbSUT5 exhibited a strong selectivity for Suc and high Suc affinities in X. laevis oocytes at pH 5—SbSUT1, 6.3 ± 0.7 mm, and SbSUT5, 2.4 ± 0.5 mm Suc. The Suc affinity of SbSUT1 was dependent on membrane potential and pH. In contrast, SbSUT5 Suc affinity was independent of membrane potential and pH but supported high transport rates at neutral pH. Suc transport by the tonoplast localized SbSUT4 could not be detected using yeast or X. laevis oocytes. Across internode development, SUTs, other than SbSUT4, were immunolocalized to sieve elements, while for elongating and recently elongated internodes, SUTs also were detected in storage parenchyma cells. We conclude that apoplasmic Suc unloading from de-energized protophloem sieve elements in meristematic zones may be mediated by reversal of SbSUT1 and/or by uniporting SWEETs. Storage parenchyma localized SbSUT1 and SbSUT5 may accumulate Suc from the stem apoplasms of elongating and recently elongated internodes, whereas SbSUT4 may function to release Suc from vacuoles. Transiting from an apoplasmic to symplasmic unloading pathway as the stem matures, SbSUT1 and SbSUT5 increasingly function in Suc retrieval into metaphloem sieve elements to maintain a high turgor to drive symplasmic unloading by bulk flow.]]> Thu 22 Nov 2018 16:43:24 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:31279 Sorghum bicolor, was evaluated during different stages of internode development. Transcript levels and functional properties of selected key transporters were measured, with both cellular and subcellular localization determined.]]> Thu 22 Nov 2018 16:23:38 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:33146 Poaceae family of grasses, namely; maize (Zea mays L.), wheat (Triticum aestivum L.) and rice (Oryza sativa L.). It is, therefore, of significant concern that all three of these Poaceae grass species are susceptible to a range of abiotic stresses, including drought and salt stress. Highly conserved among monocotyledonous and dicotyledonous plant species, microRNAs (miRNAs) are now well-established master regulators of gene expression, influencing all aspects of plant development, mediating defense responses against pathogens and adaptation to environmental stress. Here we investigate the variation in the abundance profiles of six known abiotic stress-responsive miRNAs, following exposure to salt and drought stress across these three key Poaceae grass crop species as well as to compare these profiles to those obtained from the well-established genetic model plant species, Arabidopsis thaliana (L.) Heynh. Additionally, we outline the variables that are the most likely primary contributors to instances of differential miRNA abundance across the assessed species following drought or salt stress exposure, specifically; (1) identifying variations in the experimental conditions and/or methodology used to assess miRNA abundance, and; (2) the distribution of regulatory transcription factor binding sites within the putative promoter region of a MICRORNA (MIR) gene that encodes the highly conserved, stress-responsive miRNA. We also discuss the emerging role that non-conserved, species-specific miRNAs play in mediating a plant’s response to drought or salt stress.]]> Thu 21 Oct 2021 12:52:38 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:37780 Arabidopsis thaliana (Arabidopsis) can be readily molecularly manipulated, therefore offering an excellent experimental system to alter the profile of abiotic stress responsive miRNA/target gene expression modules to determine whether such modification enables Arabidopsis to express an altered abiotic stress response phenotype. Towards this goal, high throughput sequencing was used to profile the miRNA landscape of Arabidopsis whole seedlings exposed to heat, drought and salt stress, and identified 121, 123 and 118 miRNAs with a greater than 2-fold altered abundance, respectively. Quantitative reverse transcriptase polymerase chain reaction (RT-qPCR) was next employed to experimentally validate miRNA abundance fold changes, and to document reciprocal expression trends for the target genes of miRNAs determined abiotic stress responsive. RT-qPCR also demonstrated that each miRNA/target gene expression module determined to be abiotic stress responsive in Arabidopsis whole seedlings was reflective of altered miRNA/target gene abundance in Arabidopsis root and shoot tissues post salt stress exposure. Taken together, the data presented here offers an excellent starting platform to identify the miRNA/target gene expression modules for future molecular manipulation to generate plant lines that display an altered response phenotype to abiotic stress.]]> Thu 21 Oct 2021 12:52:36 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:33857 Setaria viridis and its close domesticated relative Setaria italica have been chosen as suitable monocotyledonous models for plants possessing the C₄ pathway of photosynthesis including sorghum, maize, sugarcane, switchgrass and Miscanthus×giganteus. Accurate partial least squares regression (PLSR) models to predict S. italica stem composition have been generated, based upon Fourier transform mid-infrared (FTIR) spectra and calibrated with wet chemistry determinations of ground S. italica stem material measured using a modified version of the US National Renewable Energy Laboratory (NREL) acid hydrolysis protocol. The models facilitated a high-throughput screening analysis for glucan, xylan, Klason lignin and acid soluble lignin (ASL) in a collection of 183 natural S. italica variants and clustered them into classes, some possessing unique chemotypes. The predictive models provide a highly efficient screening tool for large scale breeding programs aimed at identifying lines or mutants possessing unique cell wall chemotypes. Genes encoding key catalytic enzymes of the lignin biosynthesis pathway exhibit a high level of conservation with matching expression profiles, measured by RT-qPCR, among accessions of S. italica, which closely mirror profiles observed in the different developmental regions of an elongating internode of S. viridis by RNASeq.]]> Thu 21 Oct 2021 12:52:27 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:10167 Sat 24 Mar 2018 08:12:27 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:11116 Sat 24 Mar 2018 08:12:26 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:17119 Sat 24 Mar 2018 08:02:29 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:17882 Sat 24 Mar 2018 07:56:19 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:26365 Sorghum bicolor(L.) Moench were deduced from histochemical determinations of cell wall composition and from the relative radial mobilities of fluorescent tracer dyes exiting vascular pipelines. The cell walls of small vascular bundles in source leaves, the predicted site of phloem loading, contained minimal quantities of lignin and suberin. A phloem-loaded symplasmic tracer, carboxyfluorescein, was retained within the collection phloem, indicating symplasmic isolation. Together, these findings suggested that phloem loading in source leaves occurs apoplasmically. Lignin was restricted to the walls of protoxylem elements located in meristematic, elongating and recently elongated regions of the stem. The apoplasmic tracer, 8-hydroxypyrene-1,3,6-trisulfonic acid, moved radially from the transpiration stream, consistent with phloem and storage parenchyma cells being interconnected by an apoplasmic pathway. The major phase of sucrose accumulation in mature stems coincided with heavy lignification and suberisation of sclerenchyma sheath cell walls restricting apoplasmic tracer movement from the phloem to storage parenchyma apoplasms. Phloem unloading at this stage of stem development followed a symplasmic route linking sieve elements and storage parenchyma cells, as confirmed by the phloem-delivered symplasmic tracer, 8-hydroxypyrene-1,3,6-trisulfonic acid, moving radially from the stem phloem.]]> Sat 24 Mar 2018 07:33:08 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:45090 Setaria viridis (green foxtail) has been identified as a potential experimental model system to genetically and molecularly characterise the C4 monocotyledonous grasses due to its small physical size, short generation time and prolific seed production, together with a sequenced and annotated genome. Setaria viridis is the wild ancestor of the cropping species, foxtail millet (Setaria italica), with both Setaria species sharing a close evolutionary relationship with the agronomically important species, maize, sorghum, and sugarcane, as well as the bioenergy feedstocks, switchgrass, and Miscanthus. However, an efficient and reproducible transformation protocol is required to further advance the use of S. viridis to study the molecular genetics of C4 monocotyledonous grasses. An efficient and reproducible protocol was established for Agrobacterium tumefaciens-mediated transformation of S. viridis (Accession A10) regenerable callus material derived from mature seeds, a protocol that returned an average transformation efficiency of 6.3%. The efficiency of this protocol was the result of the: (i) use of mature embryo derived callus material; (ii) age of the seed used to induce callus formation; (iii) composition of the callus induction media, including the addition of the ethylene inhibitor, silver nitrate; (iv) use of a co-cultivation approach, and; (v) concentration of the selective agent. Our protocol furthers the use of S. viridis as an experimental model system to study the molecular genetics of C4 monocotyledonous grasses for the potential future development of improved C4 cropping species.]]> Mon 29 Jan 2024 18:01:50 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:35166 Setaria viridis) has recently been proposed as a potential experimental model for the study of C₄ photosynthesis and is closely related to many economically important crop species of the Panicoideae subfamily of grasses, including Zea mays (maize), Sorghum bicolor (sorghum) and Sacchurum officinarum (sugarcane). Setaria viridis (Accession 10) possesses a number of key traits as an experimental model, namely; (i) a small sized, sequenced and well annotated genome; (ii) short stature and generation time; (iii) prolific seed production, and, (iv) is amendable to Agrobacterium tumefaciens-mediated transformation. There is currently however, a lack of reference gene expression information for Setaria viridis (S. viridis). We therefore aimed to identify a cohort of suitable S. viridis reference genes for accurate and reliable normalisation of S. viridis RT-qPCR expression data. Results: Eleven putative candidate reference genes were identified and examined across thirteen different S. viridis tissues. Of these, the geNorm and NormFinder analysis software identified SERINE/THERONINE-PROTEIN PHOSPHATASE 2A (PP2A), 5'-ADENYLYLSULFATE REDUCTASE 6 (ASPR6) and DUAL SPECIFICITY PHOSPHATASE (DUSP) as the most suitable combination of reference genes for the accurate and reliable normalisation of S. viridis RT-qPCR expression data. To demonstrate the suitability of the three selected reference genes, PP2A, ASPR6 and DUSP, were used to normalise the expression of CINNAMYL ALCOHOL DEHYDROGENASE (CAD) genes across the same tissues. Conclusions: This approach readily demonstrated the suitably of the three selected reference genes for the accurate and reliable normalisation of S. viridis RT-qPCR expression data. Further, the work reported here forms a highly useful platform for future gene expression quantification in S. viridis and can also be potentially directly translatable to other closely related and agronomically important C₄ crop species.]]> Mon 24 Jun 2019 16:46:06 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:18045 Mon 22 Jun 2015 10:02:57 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:53263 Mon 20 Nov 2023 12:14:18 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:37779 4) transporters. PHO2 is itself under tight regulation by the PO₄ responsive microRNA (miRNA), miR399. The DOUBLE-STRANDED RNA BINDING (DRB) proteins, DRB1, DRB2 and DRB4, have each been assigned a specific functional role in the Arabidopsis thaliana (Arabidopsis) miRNA pathway. Here, we assessed the requirement of DRB1, DRB2 and DRB4 to regulate the miR399/PHO2 expression module under PO₄ starvations conditions. Via the phenotypic and molecular assessment of the knockout mutant plant lines, drb1, drb2 and drb4, we show here that; (1) DRB1 and DRB2 are required to maintain P homeostasis in Arabidopsis shoot and root tissues; (2) DRB1 is the primary DRB required for miR399 production; (3) DRB2 and DRB4 play secondary roles in regulating miR399 production, and; (4) miR399 appears to direct expression regulation of the PHO2 transcript via both an mRNA cleavage and translational repression mode of RNA silencing. Together, the hierarchical contribution of DRB1, DRB2 and DRB4 demonstrated here to be required for the appropriate regulation of the miR399/PHO2 expression module identifies the extreme importance of P homeostasis maintenance in Arabidopsis to ensure that numerous vital cellular processes are maintained across Arabidopsis tissues under a changing cellular environment.]]> Mon 19 Apr 2021 11:56:05 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:42812 Mon 05 Sep 2022 10:04:27 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:49409 Fri 12 May 2023 14:55:34 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:43007 Fri 09 Sep 2022 14:24:20 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:49797 Fri 02 Jun 2023 17:08:29 AEST ]]>