Genome-wide identification following functional analysis of amino acid permease and cationic amino acid transporter gene families in maize and their role in drought stress

In maize, the amino acid permease (AAP) and the cationic amino acid transporters (CAT) play a significant role in amino nitrogen (N) uptake, transport, utilization, and homeostasis. Hence, genome-wide analysis of maize AAP and CAT resulted in 24 AAP (1-24) and 14 CAT (1-14) proteins in maize having significant variation in molecular weights. Most proteins are basic and localized in the plasma membrane. AAPs and CATs showed up to 7 and 14 introns respectively. All proteins showed multiple motifs, alpha-helices, transmembrane helices (except ZmAAP23), and coiled in nature. The ZmAAP and ZmCAT promoters consisted of phytohormone, plant growth and development, and stress-related cis-elements. All genes are distributed in different chromosomes. All the above properties are consistent with the same in Arabidopsis, which represent their functional similarities. Significantly higher transcription of some AAPs and CATs in vegetative and/or reproductive tissues reveal their great potential to source-sink transport and reuptake of leaked amino N from the rhizosphere. Interestingly, some members of the above-mentioned families are also upregulated during drought stress revealing their great role in drought tolerance or acclimatization during the stress. For increasing drought tolerance, these transporters might interact with the genes regulating the turgor pressure of the guard cells for increasing stomatal closure and reducing transpiration in leaves through controlling cellular osmotic homeostasis.