PARSLEY: Uses, Side Effects, Interactions and Warnings - …
The regeneration of whole plants from carrot somatic cells has been fascinated plant researchers since the 1950s, leading to the discovery of a wide variety of plant species that are capable to regenerate at levels from the single cell to major parts of the body. Numerous regeneration studies have demonstrated that the application of different concentration ratios of two plant hormones, auxin and cytokinin, leads to distinct regenerative pathways: a high cytokinin/auxin ratio will stimulate the regeneration of stems, leaves, and flower buds, and a high auxin/cytokinin ratio will induce root formation. The underlying molecular and cellular mechanisms for plant regeneration, however, remain poorly understood.
The Regional Institute - Publications
Inrecent decades, with the advances of new technologies, many genomes of economiccrop plants (several tens of them) have been sequenced and assembled. Theavailability of these sequenced genomes allows us to conduct more explicit andcutting-edge investigations that enable scientists to effectively deciphermolecular mechanisms related to the domestication and improvement of these cropplants. For example, upon assembly and analysis in allotetraploid genome ofextensively grown Upland cotton () with componentdiploid genomes of its probable progenitors, cultivated cotton ()and wild cotton (), differential regulation of plant hormoneethylene and cellulose biosynthesis were observed on the cell wall expansion ofsingle-celled natural fibers. Furthermore, comparative analysis of the cacao () genome with cotton and other genomes revealed close evolutionaryrelationships with the common ancestral paleopolyploid origin among many plantspecies. Likewise, the coffee genome provided insight into the convergentevolution of caffeine biosynthesis, the grapevine genome revealed ancestralhexaploidization while the oilseed genome was used forstudying early allopolyploid evolution. In addition, the peach () genome helped identify unique patterns of genetic diversity,domestication and evolution. The two whole genome duplication events in thepalaeopolyploid soybean () were found to be related withsignificant gene diversification, gene loss as well as chromosomerearrangements. Assembly of the cucumber () genomeresulted in unraveling a new biochemical pathway leading towards bitness, aunique taste from cucumber. Besides these and many more published draft genomesof economic crop plants, we welcome reports of any other unfinished butemerging genomes of economic importance.
To confirm the importance of root meristems for cytokinin biosynthesis, the Arabidopsis double mutant axr4-2 × aux1-7 was examined, which is impaired in the lateral root formation. The plant's total ZMP biosynthesis was not significantly altered, and the reduction caused by NAA was not significantly different from the reduction observed in WT during the same experimental conditions (data not shown). A major part of the plant's ZMP must therefore be formed in apical parts and in this mutant synthesized via the NAA-sensitive iPMP-independent pathway. The mutant's total iPMP pool, however, was reduced by 80% compared to WT. Thus a reduced root-based cytokinin biosynthesis had an impact on the plant's total iPMP content, indicating that the isopentenyl-dependent pathway dominates in the root meristems.
The involvement of the mevalonate pathway in cytokinin synthesis ..
Based on our global studies, we propose a model where auxin exercises a rapid negative control over the iPMP-independent cytokinin biosynthesis pathway that also is expressed in apical tissues. Thus, cytokinins are synthesized in both shoots and roots and preferentially in tissues rich in dividing cells, such as very young leaves and root tips. Our model also rules out cytokinin root–shoot transport as the only important mechanism maintaining shoot cytokinin pool sizes. This is in agreement with earlier studies where a paracrine mode of action for cytokinin synthesis has been suggested ().
Auxin Regulation of Cytokinin Biosynthesis Is ..
In tobacco roots, isopentenyladenine nucleotides are the major cytokinins detected (data not shown). The very low levels of ZMP and ZR in this tissue (data not shown) support the finding from Arabidopsis that mainly the iPMP-dependent pathway of cytokinin biosynthesis is present in roots. The shoot localization of the iPMP-independent pathway may be explained in terms of exclusive access of the side-chain donor in green plant tissue. The putative side-chain precursor, (2E)-4-hydroxy-3-methylbut-2-enyl diphosphate, has been identified as a key intermediate in the 2-C-methyl--erythritol 4-phosphate pathway of terpenoid biosynthesis (). This pathway, initially detected in prokaryotes, is expressed in eukaryotes that harbor plastids within their cells (). Chloroplasts might thus be a prerequisite for cytokinin biosynthesis via the alternative pathway, restricting this route of synthesis to green plant tissue.
CKbiosintesis | Adenosine Triphosphate | Biosynthesis
Small RNAs, including microRNAs (miRNAs) and siRNAs, are an extensive class of endogenous, small RNA molecules that sit at the heart of regulating gene expression in multiple developmental and signalling pathways. Recent studies have shown that climate change-induced stress, including both abiotic and biotic stresses induce aberrant expression of many small RNAs, thus suggesting that small RNAs may be a new target for genetically improving plant tolerance to certain stresses. These studies have also shown that small RNAs respond to environmental stresses in a small RNA-, stress-, tissue-, and genotype-dependent manner. During environmental stress, small RNAs function by regulating target genes within the sRNA-target gene network and by controlling signalling pathways and plant development. This symposium will focus on the current progress on this field and invite oral and poster presentations from the world wide.