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Functions manipulated by pests to obtain more resistant plants

The mechanisms which lead to disease development have been revealed by identifying the essential genes involved and whose activation leads to increased resistance against three pests of agronomic importance: nematodes, oomycetes and bacteria. A patent has been filed regarding the involvement of phytosulfokines in this mechanism.

Nematode induced feeder cells Meloidogyne incognita essential to their development cycle. Defects in the formation of these structures in the identified pskr1 mutants block the development of nematodes in female.. © Inra, Bruno Favery

How pests manipulate plant functions

Little is known about the development of diseases and particularly about the plant functions that are manipulated by pests. Root knot nematodes, oomycetes and soil-borne bacteria are pests of agronomic importance against which control methods are extremely limited. A better understanding of the development of these diseases, and particularly any common or specific elements of response, should enable the design of new control strategies. Thus inactivation of the genes essential to the development of pests in a plant, and those involved in the growth of specific feeding structures, could lead to new forms of resistance. These strategies are already effective against viruses (recessive resistance genes such as EiF4E) and some fungi (such as MLO).

Methods and research plan

To better understand the mechanisms that are disturbed in a plant subjected to biotic stresses, three classes of pests were chosen for their devastating impacts in agriculture: oomycetes (represented by Hyaloperonospora parasitica), root knot nematodes (Meloidogyne incognita) and soil-borne bacteria (Ralstonia solanacearum). R. solanacearum acts by colonising the xylem vessels that transport water and causes the plant to wilt and die. Root knot nematodes are microscopic worms present in the soil that infect numerous cultivated plants. They cause the formation of specialised feeding cells and deformities which affect the roots of infected plants. When a plant is infested by oomycetes, the latter develop intercellular hyphae and form haustoria that enable them to feed off their host.  

Involvement of PSKR1, CLV1, CLV2 and MAP65-3 proteins in the reaction to attacks

Plants with mutations of the genes disturbed when a plant is infected by these pests, and particularly during the differentiation of host cells into specialised feeding cells, display markedly increased resistance to two or even three of these pathogenic agents. These genes code for (i) the receptor for phytosulfokines, PSKR1, which are sulphated hormonal peptides involved in cell re/dedifferentiation, (ii) MAP65-3, a protein involved in the organisation of microtubule networks during nuclear division, and (iii) two CLAVATA receptors, CLV1 and CLV2, which are known for their involvement in apical meristem development.
An absence or inactivation of the PSKR1 receptor leads to differentiation defects affecting the feeding structures of oomycetes and nematodes, causing a marked reduction in their development and/or reproduction. It is important to note that the resistance endowed by PSKR1 or CLAVATA genes is not associated with impaired plant growth.

This work reveals how proteins participate in the development of disease and offer fascinating perspectives for new resistance strategies in plants. Work is now focusing on detecting mutant alleles of the PSKR1 gene in tomato and cucumber using a Tilling approach, in order to assess the resistance of these plants to pests. The results obtained relative to the PSKR1 receptor have been protected by an international patent no. WO2012/017067 regarding the use of this gene in the creation of new types of pest resistance.

Sources

  • Natalia Rodiuc et al., Evolutionary distant pathogens require the Arabidopsis phytosulfokine signalling pathway to establish disease, Plant, Cell & Environment (2016) 39,1396-1407.

For more information on the patent

WO2012017067:PLANTES RÉSISTANTES AUX PATHOGÈNES ET PROCÉDÉS POUR LA PRODUCTION DE CELLES-CI (plants resistant to pathogens and methods for production thereof)
Résumé: "La présente invention concerne des gènes de plante impliqués dans la régulation négative de la résistance à des pathogènes de plante et des utilisations de ceux-ci. Plus particulièrement,
l'invention concerne des plantes ayant une fonction phytosulfokine (PSK) déficiente et présentant une résistance augmentée à des pathogènes de plante. L'invention concerne en outre des procédés pour produire des plantes modifiées résistantes à différentes maladies. De plus, l'invention concerne des plantes ayant une fonction de récepteur PSK (PSKR) déficiente, et des procédés de criblage et d'identification de molécules qui modulent l'expression ou l'activité de PSKR".

Abstract: "The present invention relates to plant genes involved in negative regulation of resistance to plant pathogens and uses thereof. More particularly, the invention relates to plants having a defective phytosulfokine (PSK) function and exhibiting an increased resistance to plant pathogens. The invention also relates to methods for producing modified plants resistant to various diseases. Furthermore, the invention relates to plants having a defective PSK receptor (PSKR) function, and to methods of screening and identifying molecules that modulate PSKR expression or activity."

Filed by:
* GENOPLANTE – VALOR, 28 rue du docteur Finlay, Paris
Inventors:
* RODIUC, Natalia; (FR).
* MARCO, Yves; (FR).
* FAVERY, Bruno; (FR).
* KELLER, Harald; (FR).