Isolation and Characterization of Maize PMP3 Genes Involved in Salt Stress Tolerance

Abstract

Plasma membrane protein 3 (PMP3), a class of small hydrophobic polypeptides with high sequence similarity, is responsible for salt, drought, cold, and abscisic acid. These small hydrophobic ploypeptides play important roles in maintenance of ion homeostasis. In this study, eight ZmPMP3 genes were cloned from maize and responsive to salt, drought, cold and abscisic acid. The eight ZmPMP3s were membrane proteins and their sequences in trans-membrane regions were highly conserved. Phylogenetic analysis showed that they were categorized into three groups. All members of group II were responsive to ABA. Functional complementation showed that with the exception of ZmPMP3-6, all were capable of maintaining membrane potential, which in turn allows for regulation of intracellular ion homeostasis. This process was independent of the presence of Ca2+. Lastly, over-expression of ZmPMP3-1 enhanced growth of transgenic Arabidopsis under salt condition. Through expression analysis of deduced downstream genes in transgenic plants, expression levels of three ion transporter genes and four important antioxidant genes in ROS scavenging system were increased significantly in transgenic plants during salt stress. This tolerance was likely achieved through diminishing oxidative stress due to the possibility of ZmPMP3-1's involvement in regulation of ion homeostasis, and suggests that the modulation of these conserved small hydrophobic polypeptides could be an effective way to improve salt tolerance in plants.

Transgenic rice expressing a cassava (Manihot esculenta Crantz) plasma membrane gene MePMP3-2 exhibits enhanced tolerance to salt and drought stresses

“…This pattern was also conserved in MePMP3-2 ( Figure 1A). Like other PMP3 proteins (Medina et al, 2007;Fu et al, 2012), analysis of MePMP3-2 using the PHD algorithm (https://www.predictprotein.org/) (Rost et al, 2004) predicted that the two well-conserved regions of MePMP3-2 are membrane spanning domains linked by a putative hydrophilic turn, which orient both the N-and C-termini towards the apoplastic side of the membrane ( Figure 1A).…”

“…expasy.org/protparam/). The BLASTx revealed MePMP3-2 to be similar to numerous plant PMP3s including several encoded by stress-inducible genes such as LeESI3, rice OsRCI2-5, OsLti6a/b, R1G1B) (Li et al, 2014), AcPMP3-1/2, AtRCI2A/B/D/F (Medina et al, 2007), PutPMP3-1/2, and ZmPMP3-2/3/4 (Fu et al, 2012) (Figure 1A and B). In particular, these polypeptides share the…”

“…PMP3 represents a class of small hydrophobic membrane proteins that are highly conserved among species, including yeast (Navarre and Goffeau, 2000), simple animals (Medina et al, 2007), moss (Reski et al, 2004), and higher plants (Medina et al, 2007;Fu et al, 2012). In plants, multiple structural variants of PMP3 proteins exist, which are encoded by multigene families.…”

“…In plants, multiple structural variants of PMP3 proteins exist, which are encoded by multigene families. Among the abiotic stress-induced plant PMP3 genes are LeESI3 from wheatgrass (Lophopyrum elongatum), OsLti6a/b, and R1G1B from rice (Li et al, 2014), AcPMP3-1 from sheepgrass (Aneurolepidium chinense), AtRCI2A/B/D/F from Arabidopsis (Arabidopsis thaliana) (Medina et al, 2007), PutPMP3-1/-2 from alkali grass (Puccinellia tenuiflora), and ZmPMP3-2/3/4 from corn (Zea mays) (Fu et al, 2012). There is some evidence for functional specialization of plant PMP3s and of their participation in stress responses being effected in different ways.…”

“…Plant PMP3s may have similar roles, because the heterologous expression of some plant PMP3s can functionally complement yeast pmp3 mutants (Medina et al, 2007;Fu et al, 2012). Disruption of AtRCI2A increases Arabidopsis sensitivity to salt and Na + uptake while AtRCI2A over-expression has the reverse effects (Mitsuya et al, 2006); In sheepgrass, AcPMP3-1 is localized in the root cap where it regulates cytoplasmic Na + and K + accumulation.…”