Stomatal deregulation by Plasmopara viticola infection

 

 

 

Stomatal deregulation in Plasmopara viticola-infected grapevine leaves.

Allègre M., Daire X., Héloir M.-C., Trouvelot S., Mercier L., Adrian M., Pugin A. (2007)

UMR Plant Microbe Environnement INRA1088-CNRS 5184, Université de Bourgogne, 17, rue Sully, BP 86510, 21065 Dijon, France.

in New Phytol. 173(4): 832-840. – DOI: 10.1111/j.1469-8137.2006.01959.x

https://www.ncbi.nlm.nih.gov/pubmed/17286831

Abstract

In grapevine, the penetration and sporulation of Plasmopara viticola occur via stomata, suggesting functional relationships between guard cells and the pathogen. This assumption was supported by our first observation that grapevine (Vitis vinifera cv. Marselan) cuttings infected by P. viticola wilted more rapidly than healthy ones when submitted to water starvation.

Here, complementary approaches measuring stomatal conductance and infrared thermographic and microscopic observations were used to investigate stomatal opening/closure in response to infection.

In infected leaves, stomata remained open in darkness and during water stress, leading to increased transpiration. This deregulation was restricted to the colonized area, was not systemic and occurred before the appearance of symptoms.

Cytological observations indicated that stomatal lock-open was not related to mechanical forces resulting from the presence of the pathogen in the substomatal cavity.

In contrast to healthy leaves, stomatal closure in excised infected leaves could not be induced by a water deficit or abscisic acid (ABA) treatment. However, ABA induced stomatal closure in epidermal peels from infected leaves, indicating that guard cells remained functional.

These data indicate that the oomycete deregulates guard cell functioning, causing significant water losses. This effect could be attributed to a non-systemic compound, produced by the oomycete or by the infected plant, which inhibits stomatal closure or induces stomatal opening; or a reduction of the back-pressure exerted by surrounding epidermal cells.

Both hypotheses are under investigation.

Stomata and protection against downy mildew

 

Are grapevine stomata involved in the elicitor-induced protection against downy mildew?

by Allègre M., Héloir M. C., Trouvelot S., Daire X., Pugin A., Wendehenne D., Adrian M. (2009)

in Mol Plant Microbe Interact. 2009 Aug;22(8):977-86. doi: 10.1094/MPMI-22-8-0977.

Abstract

Stomata, natural pores bordered by guard cells, regulate transpiration and gas exchanges between plant leaves and the atmosphere. These natural openings also constitute a way of penetration for microorganisms. In plants, the perception of potentially pathogenic microorganisms or elicitors of defense reactions induces a cascade of events, including H(2)O(2) production, that allows the activation of defense genes, leading to defense reactions. Similar signaling events occur in guard cells in response to the perception of abscisic acid (ABA), leading to stomatal closure. Moreover, few elicitors were reported to induce stomatal closure in Arabidopsis and Vicia faba leaves. Because responses to ABA and elicitors share common signaling events, it led us to question whether stomatal movements and H(2)O(2) production in guard cells could play a key role in elicitor-induced protection against pathogens that use stomata for infection. This study was performed using the grapevine-Plasmopara viticola pathosystem. Using epidermal peels, we showed that, as for ABA, the elicitor-induced stomatal closure is mediated by reactive oxygen species (ROS) production in guard cells. In plants, we observed that the protection against downy mildew induced by some elicitors is probably not due only to effects on stomatal movements or to a guard-cell-specific activation of ROS production.

See the text: NCBI

Stomatal deregulation

 

Stomatal deregulation in Plasmopara viticola-infected grapevine leaves

by Allègre M., Daire X., Héloir M. C., Trouvelot S., Mercier L., Adrian M., Pugin A. (2007)

in New Phytol. 2007;173(4):832-40.

Abstract

In grapevine, the penetration and sporulation of Plasmopara viticola occur via stomata, suggesting functional relationships between guard cells and the pathogen. This assumption was supported by our first observation that grapevine (Vitis vinifera cv. Marselan) cuttings infected by P. viticola wilted more rapidly than healthy ones when submitted to water starvation. Here, complementary approaches measuring stomatal conductance and infrared thermographic and microscopic observations were used to investigate stomatal opening/closure in response to infection. In infected leaves, stomata remained open in darkness and during water stress, leading to increased transpiration. This deregulation was restricted to the colonized area, was not systemic and occurred before the appearance of symptoms. Cytological observations indicated that stomatal lock-open was not related to mechanical forces resulting from the presence of the pathogen in the substomatal cavity. In contrast to healthy leaves, stomatal closure in excised infected leaves could not be induced by a water deficit or abscisic acid (ABA) treatment. However, ABA induced stomatal closure in epidermal peels from infected leaves, indicating that guard cells remained functional. These data indicate that the oomycete deregulates guard cell functioning, causing significant water losses. This effect could be attributed to a nonsystemic compound, produced by the oomycete or by the infected plant, which inhibits stomatal closure or induces stomatal opening; or a reduction of the back-pressure exerted by surrounding epidermal cells. Both hypotheses are under investigation.

See the text: NCBI