The improvement of stress resilience and yield requires a detailed understanding of the effects of stress on plant reproduction. To achieve this, four important questions need to be discussed: 1. How do different environmental scenarios affect sexual reproduction and yield in different crops? 2. Which cellular processes in addition to meiosis are the most vulnerable to stress during sexual reproduction? 3. How do individual tissues and cell types respond to different stress conditions at the molecular level? 4. What are the critical defence mechanisms for survival and recovery from stress? These four questions will be addressed by three specific tasks: TASK 2.1: Determine the effects of abiotic stresses on crop reproduction. Typically, in nature abiotic stresses coincide, e.g. heat and drought. Up until now, the focus has been placed on deciphering the effects of individual stresses on plant performance, mainly in laboratory experiments. The goal to improve stress resilience of reproductive tissues and thereby yield, requires the fundamental description of the effects of different stress combinations on the physio-morphological phenotypic traits of reproductive tissues. More specifically, we will generate a phenotypic inventory including quantitative data and image compilation as a textbook for the impact of various abiotic stress scenarios on reproductive tissues, e.g. pollen viability and germination, morphological alterations in female and male 12 organs, for different crop species. This will allow the identification of the most stress sensitive traits and the determination of the key targets for improvement of stress resilience. TASK 2.2: Describe the response of reproductive tissues under stress combinations. The survival of a plant exposed to a stress incident depends on the activation of defence mechanisms that are generally called stress responses. Stress responses induce changes in all levels of regulation of gene expression which in turn ensure the synthesis of molecules (e.g. proteins, metabolites) with protective functions for macromolecules and cellular structures and which stimulate physiological reactions that minimize stress costs. Members of WG2 will compile information on the effects of different stress scenarios on the response of reproductive tissues, based on existing data derived either from – omics studies or studies on specific pathways (e.g. transcription factors, metabolic pathways, etc.). TASK 2.3: Determine the relationship of reproductive and vegetative stress resilience While an abiotic stress incident can have a direct effect on plant reproduction by affecting male and female developmental processes, stress tolerance is also dependent on the physiological status of vegetative organs. Traits that contribute to the regulation of water uptake such as root angle, primary root length, lateral root formation and root diameter can affect drought tolerance which can be exhibited in reproductive fitness, while physio-morphological adaptations of leaves and regulation of physiological processes such as transpiration and photosynthetic activity can also affect reproductive fitness under stress conditions. Members of WG2 will determine the relation of traits of vegetative tissues to the abiotic stress resilience of reproduction of crops. TASK 2.4: Identify key elements of stress resilience and their contribution to yield. WG2 will identify metabolic pathways, cellular and biological processes that are critical for stress response and tolerance and pinpoint to specific molecules across different scales (from metabolites and hormones to DNA, RNA and proteins) that play pivotal role in stress resilience during plant reproduction and yield. WG2 members will write a review in an Open Access journal regarding the molecular responses of reproductive tissues of crops on different abiotic stress combinations. The contribution of these elements for the resilience to different stress scenarios will be examined using existing or newly generated lines where their biosynthesis will be either enhanced or repressed, for example by ectopic expression of a gene or knockout mutation via CRISPR. Research groups along with private enterprises will collaborate to challenge the importance of these elements through joint experiments. We recognize that while some genes or metabolites have a universal positive impact on stress resilience across different crops, species-specific adaptation strategies require more specialized responses as well. Therefore, RECROP subgroups will join to define crop-specific responses and disseminate the results in more focused publications. A list of genes and molecules as potential primary targets for the improvement of the resilience of reproductive tissues of crops will be will be published in the webpage of RECROP.
Milestones WG2: M2.1 (Y2M3) Online phenotypic repository with stress resilient traits; M2.2 (Y3M6) Definition of important molecular responses that are related to crop reproduction resilience based on – omics datasets; M2.3 (Y4M2) Determine the stress tolerance traits of vegetative tissues that are related to reproduction resilience; M2.4 (Y4M6) Validation of functional relevance of selected genes or regulatory pathways for reproductive resilience by reverse genetics approaches by different groups; M2.5 (Y4M7) Submission of manuscript(s) with a list of genes/molecules as primary targets for crop improvement.

WG2 Contact: Marta Mendes – marta.mendes@unimi.it