Use of miPEPs to control the sunflower - orobanche interaction – miPEPiTO

Expansion of some harmful root parasitic weeds (Striga, orobanche, and Phelipanche species) in numerous economically important crops is becoming more than worrying and is a serious threat to food security in some area of Africa. If we consider the broomrape species Orobanche cumana, it causes important losses to the production of sunflower seed in countries surrounding the Black Sea, in Southern Europe and now in growing area of France. Unfortunately, no sustainable or efficient methods to control these various root parasitic weeds are presently available.
O. cumana is a holoparasite devoid of chlorophyll which is unable to carry out photosynthesis and totally relies on its host for its water, mineral, and carbohydrate supplies. Like for other species of Orobanchaceae, two key steps must be completed by this weed for establishing parasitic interaction. It must perceive specific molecular signals produced by host roots in order for its seeds to germinate, and it must develop a novel specific organ, the haustorium, to invade host root tissues and connect to host vascular system. The molecular processes underlying these two steps are largely unknown. Progress has been hampered by the lack of genomic resources in orobanche and the lack of protocols allowing reverse genetics. The objectives of the proposed project are i) to develop new molecular tools to investigate the two main steps of parasitic development and ii) to develop an innovative and sustainable biocontrol technology for management of these Orobanchaceae pests.
One partner of the project has discovered a new class of regulatory peptides, the miPEPs, which will play a pivotal role in the project. These peptides are encoded by primary transcripts of miRNAs. Each miPEP stimulates the transcription of its own encoding transcript, leading to the production of higher amount of the corresponding miRNA and consequently to a downregulation of specific target genes. This natural molecular regulation of gene expression can be obtained with synthetic miPEPs, so that specific stages of plant development can be perturbed temporally by exogenous treatment with appropriate miPEPs.
The project will consist in two main Tasks:
Task 1: to identify O. cumana miPEPs potentially involved in the regulation of seed germination/haustorium formation of O. cumana (based on RNAseq data already available and RACE-PCR analyses), to identify sunflower miPEPs most likely involved in regulating sunflower immunity (based on RNAseq data), to produce the corresponding synthetic candidate peptides and to assess the activity of O. cumana synthetic miPEPs on seed germination and haustorium differentiation (using specific and original in vitro assays).
Task 2: to select the synthetic O. cumana and sunflower miPEP candidates and evaluate their capacity to negatively affect parasitism by either decreasing broomrape growth and infection or improving sunflower resistance (using in vivo pot culture assays), and in the light of the obtained results to define the miPEPs capable of controlling two other parasitic plant – plant interactions: Phelipanche ramosa – oilseed rape and Striga hermonthica – maize.
The expected result of Task 1 is to increase our knowledge on key molecular mechanisms underlying a complex parasitic interaction by discovering important genes of O. cumana and sunflower which are involved in broomrape parasitism. The expected results of Task 2, to be exploited by a startup company, will be to provide a new phytosanitary method to control broomrape (and possibly witchweed) parasitism with highly specific and biodegradable natural substances.