Tag: Zhu J-K.

SCREAM/ICE1 and SCREAM2 and stomatal differentiation

 

SCREAM/ICE1 and SCREAM2 specify three cell-state transitional steps leading to Arabidopsis stomatal differentiation.

by Kanaoka M. M., Pillitteri L. J., Fujii H., Yoshida Y., Bogenschutz N. L., Takabayashi J., Zhu J-K., Torii K. U. (2008)

  1. Masahiro M. Kanaoka
  2. Lynn Jo Pillitteri
  3. Hiroaki Fujii
  4. Yuki Yoshida
  5. Naomi L. Bogenschutz
  6. Junji Takabayashi
  7. Jian-Kang Zhu
  8. Keiko U. Torii

in Plant Cell 20:1775–1785. – 10.1105/tpc.108.060848. –

PubMed CentralView ArticlePubMed – Abstract/FREE Full Text

Abstract

Differentiation of specialized cell types in multicellular organisms requires orchestrated actions of cell fate determinants. Stomata, valves on the plant epidermis, are formed through a series of differentiation events mediated by three closely related basic-helix-loop-helix proteins: SPEECHLESS (SPCH), MUTE, and FAMA. However, it is not known what mechanism coordinates their actions.

Here, we identify two paralogous proteins, SCREAM (SCRM) and SCRM2, which directly interact with and specify the sequential actions of SPCH, MUTE, and FAMA. The gain-of-function mutation in SCRM exhibited constitutive stomatal differentiation in the epidermis.

Conversely, successive loss of SCRM and SCRM2 recapitulated the phenotypes of fama, mute, and spch, indicating that SCRM and SCRM2 together determined successive initiation, proliferation, and terminal differentiation of stomatal cell lineages.

Our findings identify the core regulatory units of stomatal differentiation and suggest a model strikingly similar to cell-type differentiation in animals.

Surprisingly, map-based cloning revealed that SCRM is INDUCER OF CBF EXPRESSION1, a master regulator of freezing tolerance, thus implicating a potential link between the transcriptional regulation of environmental adaptation and development in plants.

Active DNA demethylation and the initiation of stomatal lineage cells.

Photo credit: Nature

Figure 1: Phenotypic analysis of epidermal patterning in the ros1 and rddmutants.

(a–d) Microscopic image of cotyledon adaxial epidermal cells from 3-day-old Col (a), epf2-1 (b), ros1-4 (c) and rdd (d). Small-cell-clusters are indicated by brackets. (e) Numbers of clustered small cells and stomata for Col, epf2-1, ros1-4, rdd and rdd-2. Values are means+s.d.’s per 25,000 μm2 of 3-day-old cotyledon adaxial epidermis (n=3). Student’s t-test, *P<0.03 (significantly different from Col), **P<0.02. Images in a–d are at the same magnification. Scale bar, 30 μm.

 

Overproduction of stomatal lineage cells in Arabidopsis mutants defective in active DNA demethylation

by Yamamuro C., Miki D., Zheng Z., Ma J., Wang J., Yang Z., Dong J., Zhu J.-K. (2014)

in Nature Communications 5,Article number:4062; doi:10.1038/ncomms5062

Abstract

DNA methylation is a reversible epigenetic mark regulating genome stability and function in many eukaryotes. In Arabidopsis, active DNA demethylation depends on the function of the ROS1subfamily of genes that encode 5-methylcytosine DNA glycosylases/lyases.

ROS1-mediated DNA demethylation plays a critical role in the regulation of transgenes, transposable elements and some endogenous genes; however, there have been no reports of clear developmental phenotypes in ros1 mutant plants.

Here we report that, in the ros1 mutant, the promoter region of the peptide ligand gene EPF2 is hypermethylated, which greatly reduces EPF2 expression and thereby leads to a phenotype of overproduction of stomatal lineage cells.

EPF2 gene expression in ros1 is restored and the defective epidermal cell patterning is suppressed by mutations in genes in the RNA-directed DNA methylation pathway.

Our results show that active DNA demethylation combats the activity of RNA-directed DNA methylation to influence the initiation of stomatal lineage cells.

HD-START protein, HD-START protein confers drought tolerance and reduced stomatal density

 

 

Activated expression of an Arabidopsis HD-START protein confers drought tolerance with improved root system and reduced stomatal density.

by Yu H., Chen X., Hong Y. Y., Wang Y., Xu P., Ke S. D., Liu H. Y., Zhu J. K., Oliver D. J., Xiang C. B. (2008)

in Plant Cell. 2008 Apr;20(4):1134-51. doi: 10.1105/tpc.108.058263. Epub 2008 Apr 30.

http://www.ncbi.nlm.nih.gov/pubmed/18451323?dopt=Abstract&holding=npg – ISI CAS PubMed

tpc2001134f03
Reduced Stomatal Density and Increased Water Use Efficiency of the Mutant. (A) Comparisons of adaxial epidermal imprint images of the wild type and the mutant (edt1) at the same ×200 and ×400 magnifications. (B) and (C) Comparisons of stomatal and cell density (B) and stomatal dimension (C) in the wild type and the edt1 mutant. Values are mean ± se (n = 30 plants, * P < 0.05, **P < 0.01). (D) to (F) Comparisons of photosynthesis rate (D), transpiration rate (E), and WUE (F) in the wild type and the edt1 mutant. WUE (mg photosynthate produced/g water transpired) was measured as described in Methods. Three measurements were made for each plant, and five plants were used for each line. Values are mean ± se (n = 30 plants, * P < 0.05, **P < 0.01). – http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2390749/bin/tpc2001134f03.jpg

Abstract

Drought is one of the most important environmental constraints limiting plant growth and agricultural productivity. To understand the underlying mechanism of drought tolerance and to identify genes for improving this important trait, we conducted a gain-of-function genetic screen for improved drought tolerance in Arabidopsis thaliana.

One mutant with improved drought tolerance was isolated and designated as enhanced drought tolerance1. The mutant has a more extensive root system than the wild type, with deeper roots and more lateral roots, and shows a reduced leaf stomatal density.

The mutant had higher levels of abscisic acid and Pro than the wild type and demonstrated an increased resistance to oxidative stress and high levels of superoxide dismutase. Molecular genetic analysis and recapitulation experiments showed that the enhanced drought tolerance is caused by the activated expression of a T-DNA tagged gene that encodes a putative homeodomain-START transcription factor.

Moreover, overexpressing the cDNA of the transcription factor in transgenic tobacco also conferred drought tolerance associated with improved root architecture and reduced leaf stomatal density.

Therefore, we have revealed functions of the homeodomain-START factor that were gained upon altering its expression pattern by activation tagging and provide a key regulator that may be used to improve drought tolerance in plants.

How to regulate stomatal closure ?

Stomatal guard cells co-opted an ancient ABA-dependent desiccation survival system to regulate stomatal closure.

by Lind C., Dreyer I., López-Sanjurjo E. J., von Meyer K., Ishizaki K.,  Kohchi T., Lang D., Zhao Y., Kreuzer I., Al-Rasheid K. A. S., Ronne H., Reski R., Zhu J.-K., Geiger D., Hedrich R. (2015)

in Current Biology, Volume 25, Issue 7, p928–935, 30 March 2015

Abstract

During the transition from water to land, plants had to cope with the loss of water through transpiration, the inevitable result of photosynthetic CO2 fixation on land [1, 2]. Control of transpiration became possible through the development of a new cell type: guard cells, which form stomata.

In vascular plants, stomatal regulation is mediated by the stress hormone ABA, which triggers the opening of the SnR kinase OST1-activated anion channel SLAC1 [3, 4]. To understand the evolution of this regulatory circuit, we cloned both ABA-signaling elements, SLAC1 and OST1, from a charophyte alga, a liverwort, and a moss, and functionally analyzed the channel-kinase interactions.

We were able to show that the emergence of stomata in the last common ancestor of mosses and vascular plants coincided with the origin of SLAC1-type channels capable of using the ancient ABA drought signaling kinase OST1 for regulation of stomatal closure.

Read the full paper: Current Biology