AN3 regulates water-use efficiency and drought tolerance by modulating stomatal density

an3 plants with reduced stomatal density. (a–c) Stomata of the 5th or 6th leaf abaxial epidermis in the 30‐day old an3 and wild‐type plants. Arrows indicate stomatal precursor cells. Bars = 50 μm. (d) GUS activity in the abaxial epidermis of the third rosette leaf from 8‐day old seedlings harbouring AN3pro‐GUS was analysed by histochemical staining. Bars = 50 μm. (e–h) Comparisons of the stomatal density and cell density (e, **P < 0.01); Stomatal precursor cells (f, **P < 0.01); stomatal index (number of stomata divided by the total number of epidermal cells) (g, *P < 0.05); and stomatal size (h, *P < 0.05 for stomatal length) in the wild‐type and an3 plants, respectively. Values are the mean ± SD from at least five independent seedlings.

 

Transcription co-activator Arabidopsis ANGUSTIFOLIA3 (AN3) regulates water-use efficiency and drought tolerance by modulating stomatal density and improving root architecture by the transrepression of YODA (YDA)

by Meng L.-S., Yao S.-Q. (2015)

Lai‐Sheng Meng, Shun‐Qiao Yao,

Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China

 

===

in Plant Biotechnol. J. 13 893–902 – DOI: 10.1111/pbi.12324 – 

[PubMed] [Cross Ref] – 

https://onlinelibrary.wiley.com/doi/full/10.1111/pbi.12324#support-information-section

A proposed model illustrating drought tolerance by the AN3‐YDA signalling pathway. (A) AN3 is recruited to the promoters of YDA by protein X and regulates the expression of key genes such as YDA that are required for stomatal development. (B) AN3 negatively regulates WUE by positively regulating stomatal density and transpiration through transrepression of YDA. AN3 is expressed in water‐sufficient conditions to facilitate stomatal development and is down‐regulated under water deficit to reduce transpiration, which results in drought tolerance. Water‐sufficient conditions improved root systems and resulted in significantly improved survival during drought. Solid lines indicate direct regulation, whereas dotted lines indicate either indirect regulation or regulation in an unknown manner.

Summary

One goal of modern agriculture is the improvement of plant drought tolerance and water‐use efficiency (WUE). Although stomatal density has been linked to WUE, the causal molecular mechanisms and engineered alternations of this relationship are not yet fully understood.

Moreover, YODA (YDA), which is a MAPKK kinase gene, negatively regulates stomatal development. BR‐INSENSITIVE 2 interacts with phosphorylates and inhibits YDA. However, whether YDA is modulated in the transcriptional level is still unclear.

Plants lacking ANGUSTIFOLIA3 (AN3) activity have high drought stress tolerance because of low stomatal densities and improved root architecture. Such plants also exhibit enhanced WUE through declining transpiration without a demonstrable reduction in biomass accumulation.

AN3 negatively regulated YDA expression at the transcriptional level by target‐gene analysis. Chromatin immunoprecipitation analysis indicated that AN3 was associated with a region of the YDA promoter in vivo.

YDA mutation significantly decreased the stomatal density and root length of an3 mutant, thus proving the participation of YDA in an3 drought tolerance and WUE enhancement.

These components form an AN3–YDA complex, which allows the integration of water deficit stress signalling into the production or spacing of stomata and cell proliferation, thus leading to drought tolerance and enhanced WUE.

AN3, COP1 and light‐mediated stomatal development

 

 

Arabidopsis ANGUSTIFOLIA3 (AN3) is associated with the promoter of CONSTITUTIVE PHOTOMORPHOGENIC1 (COP1) to regulate light‐mediated stomatal development

by Meng L.-S., Li C., Xu M.-K., Sun X.-D., Wan W., Cao X.-Y., Zhang J.-L., Chen K.-M. (2018)

Lai‐Sheng Meng, Cong Li, Meng‐Ke Xu, Xu‐Dong Sun, Wen Wan, Xiao‐Ying Cao,

Jin‐Lin Zhang, Kun‐Ming Chen,

===

in Plant, Cell & Environm. – Online Version of Record  –

https://onlinelibrary.wiley.com/doi/abs/10.1111/pce.13212?af=R

Abstract

Light signals are perceived by multiple photoreceptors that converge to suppress the RING E3 ubiquitin ligase CONSTITUTIVE PHOTOMORPHOGENIC1 (COP1) for the regulation of stomatal development. Thus, COP1 is a point of integration between light signaling and stomatal patterning. However, how light signaling is collected into COP1 for the production and spacing of stomata is still unknown.

Here, we report that the loss‐of‐function mutant of ANGUSTIFOLIA3 (AN3) delays asymmetric cell division, which leads to decreased stomatal index. Furthermore, overexpression of AN3 accelerates asymmetric cell division, which results in clusters of stomata. In addition, the stomatal development through AN3 regulation is mediated by light signaling.

Finally, we find that an3 is a light‐signaling mutant, and that AN3 protein is light regulated. Self‐activation by AN3 contributes to the control of AN3 expression. Thus, AN3 is a point of collection between light signaling and stomatal patterning.

Target‐gene analysis indicates that AN3 is associated with COP1promoter for the regulation of light‐controlling stomatal development. Together, these components for regulating stomatal development form an AN3–COP1–E3 ubiquitin ligase complex, allowing the integration of light signaling into the production and spacing of stomata.