Identification and Expression Analysis of the Isopentenyl Transferase (IPT) Gene Family under Lack of Nitrogen Stress in Oilseed (Brassica napus L.)

Abstract

BnIPT gene family members in Brassica napus and analyzing their expression under different exogenous hormones and abiotic stress treatments to provide a theoretical basis for clarifying their functions and molecular genetic mechanisms in nitrogen deficiency stress tolerance of B. napus. Using the Arabidopsis IPT protein as the seed sequence, combined with the IPT protein domain PF01715, 26 members of the BnIPT gene family were identified from the whole genome of the rape variety ZS11. Additionally, the physicochemical properties and structures, phylogenetic relationships, synteny relationships, protein-protein interaction network, and gene ontology enrichment were analyzed. Based on transcriptome data, the expression patterns of the BnIPT gene under different exogenous hormone and abiotic stress treatments were analyzed. We used the qPCR method to identify the relative expression level of BnIPT genes that may be related to the stress resistance of rapeseed in transcriptome analysis under normal nitrogen (N: 6 mmol·L^-1) and nitrogen deficiency (N: 0) conditions and analyzed its effect on rapeseed under nitrogen deficiency stress role in tolerance. In response to nitrogen deficiency signals, the BnIPT gene showed a trend of up-regulation in shoots and down-regulation in roots, indicating that it may affect the process of nitrogen transport and redistribution to enhance the stress resistance of rapeseed to respond to the nitrogen deficiency stress. This study provides a theoretical basis for clarifying the function and molecular genetic mechanism of the BnIPT gene family in nitrogen deficiency stress tolerance in rape.

Keywords: Brassica napus; IPT gene family; abiotic stress tolerance; nitrogen.

Figure 1

Chromosomal location of the BnIPTs in the B. napus genome.

Figure 2

Phylogenetic tree of IPT proteins in B. napus, A. Thaliana, and O. sativa.

Figure 3

Gene structure analysis of IPT family in B.napus. (A) Phylogenetic tree of BnIPT family. (B) Conserved motifs of BnIPT family proteins. (C) Structure of BnIPT family protein Pfam. (D) Promoter cis-acting element of BnIPT family. (E) The mRNA structure encoded by the BnIPT family.

Figure 4

Collinearity of IPT genes in B. napus, B. rapa, and B. oleracea.

Figure 5

Collinearity of BnIPT genes. The circles in the figure from inside to outside represent the unknown base N ratio, gene density, GC ratio, GC skew, and chromosome length of the B. napus genome.

Figure 6

BnIPT proteins interaction network analysis.

Figure 7

GO enrichment analysis of BnIPT genes.

Figure 8

Analysis of expression patterns of BnIPTs under exogenous hormone and abiotic stress treatments. (A) The expression levels of BnIPTs in leaf and root under CK, IAA, ACC, GAs, ABA, TZ, JA, and BL treatments. (B) The expression levels of BnIPTs in leaf and root under CK, salt, drought, freezing, cold, heat, and osmotic treatments.

Figure 9

Growth in seedling stage of B. napus under two nitrogen levels.

Figure 10

Root morphological indexes under two nitrogen levels in seedling stage of B. napus. RL: total root length, RD: decreased the mean root diameter, RT: the number of root tips, and RV: root volume. *: significant differences between treatments at p ≤ 0.05. **: significant differences between treatments at p ≤ 0.01.

Figure 11

The relative expression of BnIPT2, BnIPT5, BnIPT8, BnIPT12, BnIPT15, BnIPT18, BnIPT21, BnIPT22, and BnIPT25 in shoots (S) and roots (R) under normal nitrogen (NN) and lack of nitrogen (LN) conditions. ns: no significant differences between treatments. *: significant differences between treatments at p ≤ 0.05. **: significant differences between treatments at p ≤ 0.01.

Figure 12

Mechanism of BnIPTs on root growth of rape.