Genome-Wide Identification and Function of Aquaporin Genes During Dormancy and Sprouting Periods of Kernel-Using Apricot (Prunus armeniaca L.)

Abstract

Aquaporins (AQPs) are essential channel proteins that play a major role in plant growth and development, regulate plant water homeostasis, and transport uncharged solutes across biological membranes. In this study, 33 AQP genes were systematically identified from the kernel-using apricot (Prunus armeniaca L.) genome and divided into five subfamilies based on phylogenetic analyses. A total of 14 collinear blocks containing AQP genes between P. armeniaca and Arabidopsis thaliana were identified by synteny analysis, and 30 collinear blocks were identified between P. armeniaca and P. persica. Gene structure and conserved functional motif analyses indicated that the PaAQPs exhibit a conserved exon-intron pattern and that conserved motifs are present within members of each subfamily. Physiological mechanism prediction based on the aromatic/arginine selectivity filter, Froger’s positions, and three-dimensional (3D) protein model construction revealed marked differences in substrate specificity between the members of the five subfamilies of PaAQPs. Promoter analysis of the PaAQP genes for conserved regulatory elements suggested a greater abundance of cis-elements involved in light, hormone, and stress responses, which may reflect the differences in expression patterns of PaAQPs and their various functions associated with plant development and abiotic stress responses. Gene expression patterns of PaAQPs showed that PaPIP1-3, PaPIP2-1, and PaTIP1-1 were highly expressed in flower buds during the dormancy and sprouting stages of P. armeniaca. A PaAQP coexpression network showed that PaAQPs were coexpressed with 14 cold resistance genes and with 16 cold stress-associated genes. The expression pattern of 70% of the PaAQPs coexpressed with cold stress resistance genes was consistent with the four periods [Physiological dormancy (PD), ecological dormancy (ED), sprouting period (SP), and germination stage (GS)] of flower buds of P. armeniaca. Detection of the transient expression of GFP-tagged PaPIP1-1, PaPIP2-3, PaSIP1-3, PaXIP1-2, PaNIP6-1, and PaTIP1-1 revealed that the fusion proteins localized to the plasma membrane. Predictions of an A. thaliana ortholog-based protein–protein interaction network indicated that PaAQP proteins had complex relationships with the cold tolerance pathway, PaNIP6-1 could interact with WRKY6, PaTIP1-1 could interact with TSPO, and PaPIP2-1 could interact with ATHATPLC1G. Interestingly, overexpression of PaPIP1-3 and PaTIP1-1 increased the cold tolerance of and protein accumulation in yeast. Compared with wild-type plants, PaPIP1-3- and PaTIP1-1-overexpressing (OE) Arabidopsis plants exhibited greater tolerance to cold stress, as evidenced by better growth and greater antioxidative enzyme activities. Overall, our study provides insights into the interaction networks, expression patterns, and functional analysis of PaAQP genes in P. armeniaca L. and contributes to the further functional characterization of PaAQPs.

Decoding VaCOLD1 Function in Grapevines: A Membrane Protein Enhancing Cold Stress Tolerance

“…Single or co-overexpression of genes in yeast to test their effects on abiotic stressors is a tried-and-true method, as shown by a number of research studies. , Individually or in combination, the genes VaCOLD1 and VaGPA1 were introduced into yeast expression vectors and subsequently transformed into W303 (Figure A) to examine their functions in cold tolerance. Under normal circumstances, growth of both nontransformed and transgenic strains was comparable (Figure B,C).…”

Identification and Characterization of Salt- and Drought-Responsive AQP Family Genes in Medicagosativa L.

“…Further, in Arabidopsis [ 12 ], the PIP subfamily had the most AQP members with 13 members, but in M. sativa , the TIP subfamily had the most AQP members, with 17 members ( Table 1 ), which may be the main reason for the expansion of the AQP gene family in M. sativa . It is interesting that XIPs were identified from some plants, such as the common bean, nicotiana glauca , tea plant, apricot [ 20 , 21 , 23 , 46 ], however, XIP was absent in M. sativa as in Arabidopsis and Brassica rapa [ 12 , 31 ], which indicated that XIPs might be unique for specific families of plant.…”

“…In addition, we found that almost one third of total MsAQP proteins lost one or more of the conserved domains, at least one to three transmembrane domains or one NPA domain ( Figure S1 ). By contrast, the length of the deduced AQP proteins ranged from 240 to 323 aa in A. thaliana [ 12 ], from 219 to 329 aa in apricots [ 21 ], 236 to 326 aa in tea plants [ 20 ]. Even in the close relative of M. truncatula , the length of the majority of MtAQPs fell into the range of 218–330 aa ( Table S1 ), therefore, we suspected that the lack of partial gene sequences may be due to the incompleteness of the genome assembly.…”

“…The transport properties of the SIPs are not yet known, but the high amount of sequence divergence argues that they may have evolved separately from an ancestral gene [ 10 , 11 ]. XIPs are reported in some plant species, such as the tea plant and apricot [ 20 , 21 ], but not in the model plants such as A. thaliana or rice [ 11 , 12 ], and their functions are not very clear so far.…”

“…AQP are a large gene family in plants, and at least 35 different AQP genes were identified in A. thaliana, 31 in Zea mays and 33 in Oryza sativa [ 10 , 11 , 12 ], and the functions of many AQP genes have been characterized in different plant species, including Camellia sinensis , Prunus armeniaca , Brassica rapa , Nicotiana tabacum , Fragaria ananassa , and Triticum turgidum [ 20 , 21 , 22 , 23 , 24 , 25 ]. These AQP proteins were assumed to participate in different physiological processes, including the restriction of low pH-regulated rootlet water uptake [ 26 ], water use efficiency, hydraulic conductivity and photosynthesis [ 27 ].…”