doi: bioRxiv preprint crossover pathways that rely on the activity of FANCM, RECQ4 and FIGL1, respectively. RECQ4 appears to be the most important anti-crossover factor, as the mutation of the corresponding genes (RECQ4A and RECQ4B) led to an almost fourfold increase in recombination in Arabidopsis hybrids 2,10 . RECQ4 is a DNA helicase homologue of mammalian BLOOM and yeast Sgs1 11,12 . FANCM, which encodes another conserved DNA helicase, is also an important anti-crossover factor in Arabidopsis. Mutation of this gene also leads to a large increase in recombination, but only in pure lines (~3-fold) with a very limited effect in hybrids 2,3,5,13 . FANCM was also shown to limit crossovers in a Brassica rapa pure line 14 . The third pathway depends on the AAA-ATPase FIGL1. Mutation in FIGL1 alone leads to a relatively modest increase in recombination (+25% in Arabidopsis hybrids), but when combined with recq4 2 it leads to an almost eight-fold increase. Mutation in FIGL1 leads to full sterility in rice 15 , raising doubts about the pertinence of manipulating this gene in crop species.Here we tested the effect of recq4, fancm and figl1 mutations on recombination in three crop species. We chose rice (Oryza sativa), the cultivated pea (Pisum sativum) and tomato (Solanum lycopersium) for their economic importance and because they represent distant clades. Indeed they are members of the three major clades of flowering plants, monocots, eudicots rosids and eudicots asterids, respectively 16 . Rice is the staple of more than half of mankind and as such is the number one cereal consumed. It belongs to the Poaceae family that also contains maize, wheat and barley 16 . Pea, in addition to be the genetic model used by Mendel, is the second most cultivated pulse crop in the world (http://faostat.fao.org/) and belongs to the Fabaceae family that contains many crop species such as chickpea, beans and lentil.Tomato, the second most cultivated fresh-market vegetable crop, is one of the most .

The thick cuticle covering and embedding the epidermal cells of tomato (Solanum lycopersicum) fruit acts not only as a protective barrier against pathogens and water loss but also influences quality traits such as brightness and postharvest shelf-life. In a recent study, we screened a mutant collection of the miniature tomato cultivar Micro-Tom and isolated several glossy fruit mutants in which the abundance of cutin, the polyester component of the cuticle, was strongly reduced. We employed a newly developed mapping-by-sequencing strategy to identify the causal mutation underlying the cutin deficiency in a mutant thereafter named gpat6-a (for glycerol-3-phosphate acyltransferase6). To this end, a backcross population (BC 1 F 2 ) segregating for the glossy trait was phenotyped. Individuals displaying either a wild-type or a glossy fruit trait were then pooled into bulked populations and submitted to whole-genome sequencing prior to mutation frequency analysis. This revealed that the causal point mutation in the gpat6-a mutant introduces a charged amino acid adjacent to the active site of a GPAT6 enzyme. We further showed that this mutation completely abolished the GPAT activity of the recombinant protein. The gpat6-a mutant showed perturbed pollen formation but, unlike a gpat6 mutant of Arabidopsis (Arabidopsis thaliana), was not male sterile. The most striking phenotype was observed in the mutant fruit, where cuticle thickness, composition, and properties were altered. RNA sequencing analysis highlighted the main processes and pathways that were affected by the mutation at the transcriptional level, which included those associated with lipid, secondary metabolite, and cell wall biosynthesis.

The cuticle is a protective layer synthesized by epidermal cells of the plants and consisting of cutin covered and filled by waxes. In tomato (Solanum lycopersicum) fruit, the thick cuticle embedding epidermal cells has crucial roles in the control of pathogens, water loss, cracking, postharvest shelf-life, and brightness. To identify tomato mutants with modified cuticle composition and architecture and to further decipher the relationships between fruit brightness and cuticle in tomato, we screened an ethyl methanesulfonate mutant collection in the miniature tomato cultivar Micro-Tom for mutants with altered fruit brightness. Our screen resulted in the isolation of 16 glossy and 8 dull mutants displaying changes in the amount and/or composition of wax and cutin, cuticle thickness, and surface aspect of the fruit as characterized by optical and environmental scanning electron microscopy. The main conclusions on the relationships between fruit brightness and cuticle features were as follows: (1) screening for fruit brightness is an effective way to identify tomato cuticle mutants; (2) fruit brightness is independent from wax load variations; (3) glossy mutants show either reduced or increased cutin load; and (4) dull mutants display alterations in epidermal cell number and shape. Cuticle composition analyses further allowed the identification of groups of mutants displaying remarkable cuticle changes, such as mutants with increased dicarboxylic acids in cutin. Using genetic mapping of a strong cutindeficient mutation, we discovered a novel hypomorphic allele of GDSL lipase carrying a splice junction mutation, thus highlighting the potential of tomato brightness mutants for advancing our understanding of cuticle formation in plants.