Transcriptional changes suggest a major involvement of Gibberellins in Trifolium pratense regrowth after mowing

Abstract

13Red clover (Trifolium pratense) is used worldwide as a fodder plant due its high nutritional value. In 14 response to mowing, red clover exhibits specific morphological traits to compensate the loss of 15 biomass. The morphological reaction is well described, but knowledge of the underlying molecular 16 mechanisms are still lacking. Here we characterize the molecular genetic response to mowing of red 17 clover by using comparative transcriptomics in greenhouse conditions and agriculturally used field. 18The analysis of mown and control plants revealed candidate genes possibly regulating crucial steps 19 of the genetic network governing the regrowth reaction. In addition, multiple identified gibberellic 2 20 acid (GA) related genes suggest a major role for GA in establishing the regrowth morphology of red 21 clover. Mown red clover plants showing this regrowth morphology were partially "rescued" by 22 exogenous GA application, demonstrating the influence of GA during regrowth. Our findings provide 23 insights into the physiological and genetic processes of mowing red clover, to serve as a base for red 24 clover yield improvement. 25 26 42 ability [2,17]. Unfortunately, the morphological investigations of several T. pratense populations 43 showed a correlation of persistency with non-favorable traits, like small plant size and prostrate 3 44 growth habit [18]. Moreover, most T. pratense cultivars or accessions are locally adapted and 45 require their specific local conditions to show the favored traits [19,20], which decreases the 46 stability for individual traits in breeding efforts [21]. T. pratense exhibits significant intraspecific 47 variation due to high intrapopulation genetic diversity, thus, persistence and performance in 48 response to mowing or cutting, depends on the variety, as well as developmental stage at the 49 moment of damage [22-25]. 50 Persistency can be defined as a sustained forage yield over several growing periods [26] and is a 51 complex trait influenced by a variety of abiotic and biotic factors, and the regrowth ability of a plant 52 [27]. Plants with high regrowth ability can survive more frequent and intense biomass loss and could 53 be therefore more persistent. Decapitation or biomass loss due to herbivory or mowing triggers a 54 complex reaction affected by environmental conditions, plant morphology, architecture, 55 developmental stage and genotype [22]. After decapitation, the first stress response in other 56 legumes like Medicago sativa and Pisum sativum involves the production of phytohormones: 57 cytokinine, auxin, and strigolactones [28-30]. In addition, the mobilization of energy reserves is 58 activated [31]. Phenotypic plasticity of plant architecture in combination with alterations of 59 hormone concentrations can be observed in P. sativum (pea) and T. pratense after decapitation 60 [25,30,32]. However, the molecular processes allowing plants to thrive even after an enormous loss 61 of biomass remain still unclear, even in Arabidopsis thaliana [33,34]. 62 Here, we comp...