The Importance of TOR Kinase in Plant Development

McCready, Kirsty; Spencer, Victoria; Kim, Min Soo

doi:10.3389/fpls.2020.00016

Cited by 56 publications

(44 citation statements)

References 60 publications

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“…The complex of TOR protein kinases are potent cell growth regulators in all eukaryotes. For plants, RAPTOR1 is especially considered to be the most crucial for promoting cell expansion and coordinating multicellular growth in response to external signals, such as nutrients and PGRs (Anderson and Hanson 2005 ; McCready et al 2020 ). In the present study, higher expression (according to RNA-seq analysis) of the RAPTOR1 gene was found in PT–SH.…”

Section: Discussionmentioning

confidence: 99%

“…Lower expression of this gene, though still higher than in the leaves of regenerated plants, was noted in both the OC and PT. The high expression of RAPTOR1 , called the “master regulator” (McCready et al 2020 ) may indicate the high activity of developmental processes which take place in PT–SH. Contradictory results have been reported for the callus and regenerated shoots in tomato plants (Kumari et al 2017 ).…”

Section: Discussionmentioning

confidence: 99%

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Protuberances are organized distinct regions of long-term callus: histological and transcriptomic analyses in kiwifruit

et al. 2021

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Key message Macroscopic, ultrastructural, and molecular features—like a ball shape, the presence of starch granules, and the up-regulation of genes involved in carbohydrate metabolism and secondary metabolite biosynthesis—distinguish PT regions within a callus. Abstract The modification of the mass of pluripotent cells into de novo shoot bud regeneration is highly relevant to developmental biology and for agriculture and biotechnology. This study deals with protuberances (PT), structures that appear during the organogenic long-term culturing of callus (OC) in kiwifruit. These ball-shaped regions of callus might be considered the first morphological sign of the subsequent shoot bud development. Sections of PT show the regular arrangement of some cells, especially on the surface, in contrast to the regions of OC beyond the PT. The cells of OC possess chloroplasts; however, starch granules were observed only in PTs’ plastids. Transcriptomic data revealed unique gene expression for each kind of sample: OC, PT, and PT with visible shoot buds (PT–SH). Higher expression of the gene involved in lipid (glycerol-3-phosphate acyltransferase 5 [GPAT5]), carbohydrate (granule-bound starch synthase 1 [GBSS1]), and secondary metabolite (beta-glucosidase 45 [BGL45]) pathways were detected in PT and could be proposed as the markers of these structures. The up-regulation of the regulatory associated protein of TOR (RAPTOR1) was found in PT–SH. The highest expression of the actinidain gene in leaves from two-year-old regenerated plants suggests that the synthesis of this protein takes place in fully developed organs. The findings indicate that PT and PT–SH are specific structures within OC but have more features in common with callus tissue than with organs.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Protuberances are organized distinct regions of long-term callus: histological and transcriptomic analyses in kiwifruit

et al. 2021

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“…RBR and TOR connect metabolic and auxin signaling in cell cycle regulation. TOR has been reported to regulate AR induction in Arabidopsis and potato ( Deng et al, 2017 ) and participate in meristem size regulation by controlling cell proliferation ( McCready et al, 2020 ). In addition, TOR inhibition has been reported to produce a decrease of DNA methylation affecting genes involved in hormone signaling, suggesting a role in chromatin remodeling ( Zhu et al, 2020 ).…”

Section: Identifying Molecular Checkpoints For Adventitious Rooting Cmentioning

confidence: 99%

Identifying Molecular Chechkpoints for Adventitious Root Induction: Are We Ready to Fill the Gaps?

Abarca

2021

Front. Plant Sci.

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The molecular mechanisms underlying de novo root organogenesis have been under intense study for the last decades. As new tools and resources became available, a comprehensive model connecting the processes and factors involved was developed. Separate phases that allow for specific analyses of individual checkpoints were well defined. Physiological approaches provided information on the importance of metabolic processes and long-distance signaling to balance leaf and stem status and activation of stem cell niches to form new root meristems. The study of plant hormones revealed a series of sequential roles for cytokinin and auxin, dynamically interconnected and modulated by jasmonic acid and ethylene. The identification of genes specifying cell identity uncovered a network of sequentially acting transcriptional regulators that link hormonal control to cell fate respecification. Combined results from herbaceous model plants and the study of recalcitrant woody species underscored the need to understand the limiting factors that determine adventitious rooting competence. The relevance of epigenetic control was emphasized by the identification of microRNAs and chromatin remodeling agents involved in the process. As the different players are set in place and missing pieces become apparent, findings in related processes can be used to identify new candidates to complete the picture. Molecular knobs connecting the balance cell proliferation/differentiation to hormone signaling pathways, transcriptional control of cell fate or metabolic modulation of developmental programs can offer clues to unveil new elements in the dynamics of adventitious rooting regulatory networks. Mechanisms for cell non-autonomous signaling that are well characterized in other developmental processes requiring establishment and maintenance of meristems, control of cell proliferation and cell fate specification can be further explored. Here, we discuss possible candidates and approaches to address or elude the limitations that hinder propagation programs requiring adventitious rooting.

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“…As in non-photosynthetic eukaryotes, TOR is involved in a multitude of processes in plants, including plant organ initiation, growth and patterning, translation, transcription, cell cycle control, and autophagy [ 75 , 139 , 140 , 141 , 142 , 143 , 144 , 145 , 146 , 147 , 148 ]. In the following sections, we discuss upstream and downstream TOR-autophagy signaling network components in photosynthetic organisms, including algae and land plants.…”

Section: Tor Signaling In Photosynthetic Organismsmentioning

confidence: 99%

Target of Rapamycin in Control of Autophagy: Puppet Master and Signal Integrator

Mugume

Kazibwe

Bassham

2020

IJMS

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The target of rapamycin (TOR) is an evolutionarily-conserved serine/threonine kinase that senses and integrates signals from the environment to coordinate developmental and metabolic processes. TOR senses nutrients, hormones, metabolites, and stress signals to promote cell and organ growth when conditions are favorable. However, TOR is inhibited when conditions are unfavorable, promoting catabolic processes such as autophagy. Autophagy is a macromolecular degradation pathway by which cells degrade and recycle cytoplasmic materials. TOR negatively regulates autophagy through phosphorylation of ATG13, preventing activation of the autophagy-initiating ATG1-ATG13 kinase complex. Here we review TOR complex composition and function in photosynthetic and non-photosynthetic organisms. We also review recent developments in the identification of upstream TOR activators and downstream effectors of TOR. Finally, we discuss recent developments in our understanding of the regulation of autophagy by TOR in photosynthetic organisms.

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The Importance of TOR Kinase in Plant Development

Cited by 56 publications

References 60 publications

Protuberances are organized distinct regions of long-term callus: histological and transcriptomic analyses in kiwifruit

Protuberances are organized distinct regions of long-term callus: histological and transcriptomic analyses in kiwifruit

Identifying Molecular Chechkpoints for Adventitious Root Induction: Are We Ready to Fill the Gaps?

Target of Rapamycin in Control of Autophagy: Puppet Master and Signal Integrator

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