Cucurbitaceae plants are of considerable biological and economic importance, and genomes of cucumber, watermelon, and melon have been sequenced. However, a comparative genomics exploration of their genome structures and evolution has not been available. Here, we aimed at performing a hierarchical inference of genomic homology resulted from recursive paleopolyploidizations. Unexpectedly, we found that, shortly after a core-eudicot-common hexaploidy, a cucurbit-common tetraploidization (CCT) occurred, overlooked by previous reports. Moreover, we characterized gene loss (and retention) after these respective events, which were significantly unbalanced between inferred subgenomes, and between plants after their split. The inference of a dominant subgenome and a sensitive one suggested an allotetraploid nature of the CCT. Besides, we found divergent evolutionary rates among cucurbits, and after doing rate correction, we dated the CCT to be 90–102 Ma, likely common to all Cucurbitaceae plants, showing its important role in the establishment of the plant family.

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(1975). Orientation-and direction-selectivity, as well as the responsiveness of the population of neurones, seemed unaltered. The reduction in binocularity was much less convincing for cells in the body of area 17, even very close to the callosal-recipient zone. 3. Reversible cooling of the 17/18 border had no effect on the few cells recorded outside the callosal zone in the other hemisphere nor on eighteen of the thirty-five cells recorded in the callosal zone. However, in ten cells the receptive field disappeared completely in one eye; in five cells there was a general reduction in responsiveness; two cells lost a portion of the receptive field, on the ipsilateral side, in both eyes.4. The receptive fields that were apparently transmitted via the corpus callosum lay around the vertical meridian ofthe visual field and were not restricted to the visual hemifield ipsilateral to the receiving hemisphere: their distribution overlapped that provided by the direct geniculo-cortical input.5. The principal function of the callosal projection between the 17/18 borders may be to contribute to binocular convergence on cortical cells and perhaps to play a part in stereoscopic vision.

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