Table 1

Primer sequences"

Fig. 1

Cloning, gene structure, and physicochemical property analysis of the NtCEP7 gene in tobacco A: PCR amplification of the NtCEP7 gene; M: DL500 bp DNA Marker; 1, 2: PCR products. B: gene structure of NtCEP7; C: prediction of the signal peptide of NtCEP7 pro-protein; D: nucleotide and amino acid sequences of NtCEP7 gene; *: translation termination point. E: prediction of transmembrane domains pro-protein."

Fig. 2

Phylogenetic analysis of CEP proteins and cis-acting elements in the NtCEP7 promoter in tobacco A: phylogenetic tree of the proteins of Arabidopsis thaliana (At), Solanum lycopersicum (Sl), and Nicotiana tabacum (Nt) CEP; B: analysis of cis-acting elements in promoters. ABRE: cis-acting element involved in the abscisic acid responsiveness; as-1: auxin and salicylic acid responsive element; CGTCA-motif: MeJA-responsive; TGACG-motif: MeJA-responsive; TCA-element: cis-acting element involved in salicylic acid responsiveness; TGA-element: auxin-responsive element; MYC: MYC binding site element; LTR: cis-acting element involved in low-temperature responsiveness; MYB: MYB binding site element; ARE: cis-acting regulatory element essential for the anaerobic induction; W box: the inducer, injury, and pathogen responses bind to WRKY class transcription factors; Box 4: part of the conserved DNA module of cis-acting regulatory elements involved in light response; G-Box: cis-acting regulatory element involved in light responsiveness; A-box: cis-acting regulatory element; MRE: metal response element; ACE: cis-acting element involved in light responsiveness."

Fig. 3

Expression analysis of the NtCEP7 gene in leaves and roots under drought stress T0: control; T1: dehydration at room temperature; T2: ABA treatment. *, **, and *** denote significant difference at P < 0.05, P < 0.01, and P < 0.001, respectively."

Fig. 4

Effect of the NtCEP7a peptide on drought resistance in tobacco A: analysis of tobacco plant growth status; B: analysis of leaf water content of tobacco plants; C: analysis of shoot dry weight of tobacco plants; D: analysis of root dry weight of tobacco plants; E: analysis of MDA content of tobacco plants; F: analysis of Pro content of tobacco plants; G: analysis of electrical conductivity of tobacco plants. CK: normal conditions+foliar spraying of equal volume of clear water; CK+CEP: normal conditions+foliar spraying of 1 μmol L-1 NtCEP7a peptide; D: drought conditions+foliar spraying of equal volume of clear water; D+CEP: drought conditions+foliar spraying of 1 μmol L-1 NtCEP7a peptide. Lowercase letters indicate significant differences between treatments (P < 0.05); Fig. A scale bar is 7 cm. Physiological and biochemical data were obtained from the leaves of tobacco seedlings after seven days of treatment, as shown in Fig. 4-A."

Fig. 5

Effects of NtCEP7a peptide on stomatal movement and in vitro water loss rate of leaves in tobacco A: phenotypic map of tobacco stomata; B: stomatal width to length ratio; C: leaf water loss rate in vitro. Different lowercase letters indicate statistically significant differences between treatments (P < 0.05). Scale bar = 30 μm. All physiological and biochemical data were obtained from the leaves of tobacco seedlings after seven days of treatment, as shown in Fig. 4-A. Treatments are the same as those given in Fig. 4."

Table 2

Effects of foliar application of NtCEP7a peptide on photosynthetic characteristics of tobacco under drought stress"

Fig. 6

Effects of the NtCEP7a peptide on the activities of SOD, POD, and CAT in tobacco leaves A: NBT staining; B: $\mathrm{O}_{2}^{\bar{.}}$content; C: H2O2 content; D: SOD activity; E: POD activity; F: CAT activity. Different lowercase letters indicate significant differences between treatments at P < 0.05. All physiological and biochemical data were obtained from the leaves of tobacco seedlings after seven days of treatment, as shown in Fig. 4A. Treatments are the same as those given in Fig. 4."