Stomata and the behaviour of the urediospore germtube in Melampsora larici-populina on the leaf surface of Populus purdomii

Photo credit: Google

Populus purdomii


Infection Behaviour of Melampsora larici-populina on the Leaf Surface of Populus purdomii

by Yu Z.-d., Peng S.-b., Ren Z._z., Wang D.-m., Cao Z.-m. (2011)

Zhong-dong YUShao-bing PENGZheng-zheng RENDong-mei WANGZhi-min CAO

Zhong-dong YU, Forestry College, Northwest A&F University, Jangling, 712100, P.R. China


in Agricultural Sciences in China 10(10): 1562-1569 – DOI10.1016/S1671-2927(11)60152-1 –


Behaviour of urediospore germtube in Melampsora larici-populina on the leaf surface of Populus purdomii were studied by light microscope, scanning electron microscope (SEM), transmission electron microscope (TEM), and fluorescence microscope.

Crab-like fusion cells on leaf surface, intercellular hyphal cells in leaf tissues, as well as nucleus states, were observed and counted up in this study. Under unsaturated humidity, 32% of germinated tubes fused into a distinguishable swollen crab-shaped cell at the merging site, and 10.5% of observed crab-like cells had more than three nuclei.

Wedge-shaped mycelia developed and then penetrated the leaf surface directly, or indirectly through stomata. Tips of germtube passed through the intercellular cells of poplar leaves directly were found in TEM. Aniline blue dyeing also showed that the infecting hyphae could invade into the cuticle and epidemic cell wall directly.

For the case of infection through stomata, there were two different situations. Short branches and wedge hyphae usually penetrated the leaf surface via opened stomata, whereas, some germtube branches and wedge hyphae penetrated leaves through the guard cell walls or stoma lips. In the latter case, the stomata were always closed.

The samples from wild forestlands had the same fused cells and wedge hyphae, but the occurrence rate was much higher than that in the chamber. Even under the saturated air humidity, germtubes could roll back and formed fusion structure, or merged together with their tips. The fusion cells might centralize the plasma of merged germtubes and have a strong survival capacity to protect germtubes from dying under arid circumstances, and provide a chance of genetic variation as well.


ABA inhibits entry into stomatal-lineage development



ABA inhibits entry into stomatal-lineage development in Arabidopsis leaves

by Tanaka Y., Nose T., Jikumaru Y., Kamiya Y. (2013)

Yoko TanakaTomoe NoseYusuke JikumaruYuji Kamiya

Yoko Tanaka, RIKEN Plant Science Center

Yusuke Jikumaru, RIKEN Plant Science Center, Department of Biosciences, Teikyo University


in Plant Journal 74(3): 448457 – DOI10.1111/tpj.12136


The number and density of stomata are controlled by endogenous and environmental factors. Despite recent advances in our understanding of stomatal development, mechanisms which prevent stomatal‐lineage entry remain unclear.

Here, we propose that abscisic acid (ABA), a phytohormone known to induce stomatal closure, limits initiation of stomatal development and induces enlargement of pavement cells in Arabidopsis cotyledons.

An ABA‐deficient aba2‐2 mutant had an increased number/proportion of stomata within a smaller cotyledon, as well as reduced expansion of pavement cells. This tendency was reversed after ABA application or in an ABA over‐accumulatingcyp707a1cyp707a3 doublemutant.

Our time course analysis revealed that aba2‐2 shows prolonged formation of meristemoids and guard mother cells, both precursors of stoma. This finding is in accordance with prolonged gene expression of SPCH and MUTE, master regulators for stomatal formation, indicating that ABA acts upstream of these genes.

Only aba2‐2 mute, but not aba2‐2 spch double mutant showed additive phenotypes and displayed inhibition of pavement cell enlargement with increased meristemoid number, indicating that ABA action on pavement cell expansion requires the presence of stomatal‐lineage cells.

Susceptibility of the stomata K+-uptake channel KST1 to Zn2+ requires histidine residues



Susceptibility of the guard-cell K+-uptake channel KST1 to Zn2+ requires histidine residues in the S3-S4 linker and in the channel pore

by Hoth S., Hedrich R. (1999)

Stefan HothRainer Hedrich

in Planta 209(4): 543-546 – ISSN :0032-0935 – journal e-ISSN :1432-2048 –


Potassium channels are inhibited by several mono- and divalent cations. To identify sites involved in the interaction between K+ channels and cationic effectors, we expressed the potato (Solanum tuberosum L.) guard-cell K+-uptake channel KST1 in Xenopus oocytes.

This channel was reversibly blocked by extracellular Zn2+ in the micromolar range. In the presence of this heavy metal, steady-state currents were reduced in a pH-dependent but voltage-independent manner. Since Zn2+-inhibition was less effective at elevated external proton concentrations, we generated alanine mutants with respect to both extracellular histidines in KST1.

Whereas substitution of the pore histidine H271 resulted in a reduced blockade by Zn2+, the channel mutant KST1-H160A in the S3-S4 linker lost most of its Zn2+ sensitivity.

Since both histidines alter the susceptibility of KST1 to Zn2+, the block may predominantly result from these two sites. We thus conclude that the S3-S4 linker is involved in the formation of the outer pore.

Regulatory posttranslational modification of a guard cell protein that is specifically implicated in stomatal movements.



In vivo phosphorylation of phosphoenolpyruvate carboxylase in guard cells of Vicia faba L. is enhanced by fusicoccin and suppressed by abscisic acid

by Du Z., Aghoram K., Outlaw W. H. (1997)

Zhirong DuKarthik AghoramWilliam H. Outlaw


in Archives of Biochemistry and Biophysics 337(2): 345-350 – DOI10.1006/abbi.1996.9790 –


Plants regulate water loss and CO 2 gain by modulating the aperture sizes of stomata that penetrate the epidermis. Aperture size itself is increased by osmolyte accumulation and consequent turgor increase in the pair of guard cells that flank each stoma.

Guard cell phosphoenolpyruvate carboxylase (PEPC, EC, which catalyzes the regulated step leading to malate synthesis, is crucial for charge and pH maintenance during osmolyte accumulation. Regulation of this cytosolic enzyme by effectors is well documented, but additional regulation by posttranslational modification is predicted by the alteration of PEPC kinetics during stomatal opening (FEBS Lett.352, 45-48).

In this study, we have investigated whether this alteration is associated with the phosphorylation status of this enzyme. Using sonicated epidermal peels (”isolated” guard cells) preloaded with 3 2 PO 4 , we induced stomatal opening and guard cell malate accumulation by incubation with 5 μmfusicoccin (FC).

In corroboratory experiments, guard cells were incubated with the FC antagonist, 10 μmabscisic acid (ABA). The phosphorylation status of PEPC was assessed by immunoprecipitation, electrophoresis, immunoblotting, and autoradiography. PEPC was phosphorylated when stomata were stimulated to open, and phosphorylation was lessened by incubation with ABA.

Thus, we conclude that regulation of guard cell PEPCin vivo is multifaceted; the effects of regulatory metabolites and the activation status of the enzyme are integrated to control malate synthesis.

These results, together with the coincident alteration in the kinetics of the enzyme (FEBS Lett.352, 45-48), constitute the first unequivocal demonstration of regulatory posttranslational modification of a guard cell protein that is specifically implicated in stomatal movements.

Role of the outer stomatal ledges in the mechanics of stomatal movements

Photo credit: Google

Acokanthera oblongifolia

Role of the outer stomatal ledges in the mechanics of guard cell movements

by Pautov A., Bauer S., Ivanova O., Krylova E., Sapach Y., Gussarova G. (2017)

Anatoly PautovSvetlana BauerOlga IvanovaElena KrylovaYulia SapachGalina Gussarova

Anatoly Pautov, St. Petersburg State University, Department of Botany, Faculty of Biology, St. Petersburg, Russia

Svetlana Bauer, St. Petersburg State University, Department of Hydroelasticity, Faculty of Mathematics and Mechanics, St. Petersburg, Russia

Photo credit – Carissa spectabilis – Carissa spectabilis –


in Trees 31(1): 125-135 – DOI10.1007/s00468-016-1462-x –

Key Message

The modelling showed that outer ledges prevent wide opening of the stomatal pore and its lifting above leaf epidermis. This stomatal mechanics is combined with xeromorphic features of leaf epidermis.

Photo credit Google – The flower of Exbucklandia populnea.-


Methods of light, scanning, and transmission electron microscopy were used to study the stomata of the leaf epidermis in evergreen Acokanthera oblongifolia (Apocynaceae), A. oppositifolia (Apocynaceae), Carissa spectabilis (Apocynaceae), Exbucklandia populnea (Hamamelidaceae), and Trochodendron aralioides (Trochodendraceae).

The stomata of their leaf epidermis are located on subsidiary cells, have large outer ledges, and lack inner ledges. To elucidate the role of the ledges, we applied dynamic modelling using the finite-element method. The application of dynamic modelling has shown that outer ledges prevent wide opening of the stomatal pore and their rising above the surface of leaf epidermis.

The results of the modelling are supported by the observed deformations in the guard cells of the real stomata. This stomatal mechanics is combined with such stomatal xeromorphic features as thick cuticle, stomatal cavities, and waxy plugs (in A. oblongifolia).

All studied species show similar leaf anatomy. It has much in common with the leaf anatomy of species connected in their origin with subhumid Tertiary laurophyllous forests.


Oligogalacturonides stimulate cell divisions leading to stoma formation



Oligogalacturonides stimulate pericycle cell wall thickening and cell divisions leading to stoma formation in tobacco leaf explants

by Altamura M. M., Zaghi D., Salvi G., De Lorenzo G., Bellincampi D. (1998)

Maria Maddalena AltamuraDaniela ZaghiGiovanni SalviGiulia De LorenzoDaniela Bellincampi

in Planta 204(4): 429-436 – journal ISSN :0032-0935 –

Timely MUTE expression is essential to prevent stomatal fate in SLGCs and to promote their differentiation as pavement cells.



Timely expression of the Arabidopsis stoma-fate master regulator MUTE is required for specification of other epidermal cell types.

by Triviño, M., Martín-Trillo, M., Ballesteros, I., Delgado, D., de Marcos, A., Desvoyes, B., Gutiérrez, C., Mena, M. and Fenoll, C. (2013)

Magdalena TriviñoMar Martín‐TrilloIsabel BallesterosDolores DelgadoAlberto de MarcosBénédicte DesvoyesCrisanto GutiérrezMontaña MenaCarmen Fenoll

Magdalena Triviño, Facultad de Ciencias Ambientales y Bioquímica, Universidad de Castilla la Mancha

Bénédicte Desvoyes, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas‐Universidad Autónoma de Madrid


in Plant J, 75(5): 808–822 – doi:10.1111/tpj.12244 –


Epidermal differentiation in Arabidopsis thaliana aerial organs involves stomatal lineage development. Lineages derive from meristemoids, which arise from asymmetric divisions of protodermal cells. Each meristemoid divides repeatedly in an inward spiral before it transits to a guard mother cell (GMC) that produces the stoma, leaving a trail of surrounding stomatal lineage ground cells (SLGCs) that eventually differentiate into endoreplicated pavement cells.

MUTE is a bHLH transcription factor that is expressed in late meristemoids and drives their transition to GMCs. Loss‐of‐function mute mutants are stomata‐less dwarf plants with arrested lineages, in which stunted putative SLGCs surround a halted meristemoid.

We analysed MUTE functions using a chemically inducible system for mute‐3complementation based on conditional MUTE expression in its normal domain. Continuous induction from germination produced stomata‐bearing, normal‐sized plants with viable mute‐3 seeds. In 2‐week‐old mute‐3cotyledons, meristemoids appeared to retain their identity and synchronously formed stomata in response to induced MUTE expression.

However, arrested SLGCs were not complemented: many produced stomata, leading to stomatal clusters, and others remained unexpanded and diploid. In contrast, non‐lineage pavement cells, which are under‐endoreplicated in mute‐3, expanded and increased their ploidy level upon induction, showing that the lack of response of SLGCs is specific to this arrested cell type.

Leaf phenotypic mosaics include wild‐type lineages and adjacent mute‐3 lineages, whose meristemoids and putative SLGCs remained arrested, indicating that the role of MUTE in SLGC fate is strictly lineage‐autonomous.

These results show that timely MUTE expression is essential to prevent stomatal fate in SLGCs and to promote their differentiation as pavement cells.