Abstract
Melon (Cucumis melo L.) is a very important crop throughout the world and has great economic importance, in part due to its nutritional properties. It prefers well-drained soil with low acidity and has a strong demand for water during fruit set. Therefore, a correct water balance—involving aquaporins—is necessary to maintain the plants in optimal condition. This manuscript describes the identification and comparative analysis of the complete set of aquaporins in melon. 31 aquaporin genes were identified, classified and analysed according to the evolutionary relationship of melon with related plant species. The individual role of each aquaporin in the transport of water, ions and small molecules was discussed. Finally, qPCR revealed that almost all melon aquaporins in roots and leaves were constitutively expressed. However, the high variations in expression among them point to different roles in water and solute transport, providing important features as that CmPIP1;1 is the predominant isoform and CmTIP1;1 is revealed as the most important osmoregulator in the tonoplast under optimal conditions. The results of this work pointing to the physiological importance of each individual aquaporin of melon opening a field of knowledge that deserves to be investigated.
Highlights
Aquaporins are highly conserved transmembrane proteins, present in all domains of life, whose main function is the selective, bidirectional and passive transport of water and some small neutral solutes and ions[1]
A search of the whole genome for aquaporins proteins revealed 57 matches in the National Centre of Biotechnology Information (NCBI) protein database, 34 corresponding to C. melo, while the rest of the nonselected sequences were specific to concrete varieties
The number of aquaporins genes identified in melon (31) was comparable with the number found in other plant species, such as rice (33)[49], A. thaliana (35)[2] and watermelon (35)[20]
Summary
Aquaporins are highly conserved transmembrane proteins, present in all domains of life, whose main function is the selective, bidirectional and passive transport of water and some small neutral solutes and ions[1]. These residues were described in the first years of aquaporins discovery, but they have been little studied[10,11,12] In this way, in addition to water, plant aquaporins have been investigated for their capacity to transport a wide range of solutes such as carbon dioxide (CO2), hydrogen peroxide (H2O2), short polyols like glycerol (Gly), NH3, urea, boric acid (boron, B), silicic acid (silicon, Si), arsenic (As), antimonite (Sb) and some other compounds like germanic acid, selenic acid, lactic acid, formamide and acetamide (for a detailed bibliography see Luang and Hrmova, 2017)[3]. Analysis by qPCR was carried out in roots and leaves after the design of primers and a comparison with RNA-seq results was done with existing databases
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