Plant expansins: diversity and interactions with plant cell walls

Cosgrove, Daniel J.

doi:10.1016/j.pbi.2015.05.014

Cited by 373 publications

(396 citation statements)

References 95 publications

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“…The regulation of the multigene families of cell wall remodeling families is highly complex and the emergent property of the combinatorial activities of multiple TFs. Likewise, single knockouts of expansin genes have thus far failed to yield developmental phenotypes (Cosgrove, 2015). ATHB5 therefore represents one of many upstream regulatory factors of the EXPA3 gene.…”

Section: Discussionmentioning

confidence: 99%

The Transcription Factor ATHB5 Affects GA-Mediated Plasticity in Hypocotyl Cell Growth during Seed Germination

et al. 2016

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Gibberellic acid (GA)-mediated cell expansion initiates the seed-to-seedling transition in plants and is repressed by DELLA proteins. Using digital single-cell analysis, we identified a cellular subdomain within the midhypocotyl, whose expansion drives the final step of this developmental transition under optimal conditions. Using network inference, the transcription factor ATHB5 was identified as a genetic factor whose localized expression promotes GA-mediated expansion specifically within these cells. Both this protein and its putative growth-promoting target EXPANSIN3 are repressed by DELLA, and coregulated at single-cell resolution during seed germination. The cellular domains of hormone sensitivity were explored within the Arabidopsis (Arabidopsis thaliana) embryo by putting seeds under GAlimiting conditions and quantifying cellular growth responses. The middle and upper hypocotyl have a greater requirement for GA to promote cell expansion than the lower embryo axis. Under these conditions, germination was still completed following enhanced growth within the radicle and lower axis. Under GA-limiting conditions, the athb5 mutant did not show a phenotype at the level of seed germination, but it did at a cellular level with reduced cell expansion in the hypocotyl relative to the wild type. These data reveal that the spatiotemporal cell expansion events driving this transition are not determinate, and the conditional use of GA-ATHB5-mediated hypocotyl growth under optimal conditions may be used to optionally support rapid seedling growth. This study demonstrates that multiple genetic and spatiotemporal cell expansion mechanisms underlie the seed to seedling transition in Arabidopsis.

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Section: Discussionmentioning

confidence: 99%

The Transcription Factor ATHB5 Affects GA-Mediated Plasticity in Hypocotyl Cell Growth during Seed Germination

et al. 2016

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“…However, this term usually implies a chemical change in covalent bonding within the cell wall, which does not appear to be necessary for cell wall creep, i.e. a-expansin facilitates cell wall creep without evidence of hydrolysis or other covalent modification of wall polymers (Cosgrove, 2015(Cosgrove, , 2016a. I use wall "softening" to denote a process that changes wall stiffness, without the implication that the wall can grow more quickly.…”

Section: Wall Stress Relaxation Drives Cell Growthmentioning

confidence: 99%

Diffuse Growth of Plant Cell Walls

2017

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“…and Cosgrove, 2005;Cosgrove, 2015). Expansin genes are also found in a variety of bacteria, fungi, and other microbes (Darley et al, 2003;Georgelis et al, 2014), acquired by horizontal gene transfer from plants .…”

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confidence: 99%

The Target of β-Expansin EXPB1 in Maize Cell Walls from Binding and Solid-State NMR Studies

et al. 2016

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The wall-loosening actions of b-expansins are known primarily from studies of EXPB1 extracted from maize (Zea mays) pollen. EXPB1 selectively loosens cell walls (CWs) of grasses, but its specific binding target is unknown. We characterized EXPB1 binding to sequentially extracted maize CWs, finding that the protein primarily binds glucuronoarabinoxylan (GAX), the major matrix polysaccharide in grass CWs. This binding is strongly reduced by salts, indicating that it is predominantly electrostatic in nature. For direct molecular evidence of EXPB1 binding, we conducted solid-state nuclear magnetic resonance experiments using paramagnetic relaxation enhancement (PRE), which is sensitive to distances between unpaired electrons and nuclei. By mixing 13 C-enriched maize CWs with EXPB1 functionalized with a Mn 2+ tag, we measured Mn 2+ -induced PRE. Strong 1 H and 13 C PREs were observed for the carboxyls of GAX, followed by more moderate PREs for carboxyl groups in homogalacturonan and rhamnogalacturonan-I, indicating that EXPB1 preferentially binds GAX. In contrast, no PRE was observed for cellulose, indicating very weak interaction of EXPB1 with cellulose. Dynamics experiments show that EXPB1 changes GAX mobility in a complex manner: the rigid fraction of GAX became more rigid upon EXPB1 binding while the dynamic fraction became more mobile. Combining these data with previous results, we propose that EXPB1 loosens grass CWs by disrupting noncovalent junctions between highly substituted GAX and GAX of low substitution, which binds cellulose. This study provides molecular evidence of b-expansin's target in grass CWs and demonstrates a new strategy for investigating ligand binding for proteins that are difficult to express heterologously.

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Plant expansins: diversity and interactions with plant cell walls

Cited by 373 publications

References 95 publications

The Transcription Factor ATHB5 Affects GA-Mediated Plasticity in Hypocotyl Cell Growth during Seed Germination

The Transcription Factor ATHB5 Affects GA-Mediated Plasticity in Hypocotyl Cell Growth during Seed Germination

Diffuse Growth of Plant Cell Walls

The Target of β-Expansin EXPB1 in Maize Cell Walls from Binding and Solid-State NMR Studies

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