Bioinformatics Study of Aux/IAA Family Genes and Their Expression in Response to Different Hormones Treatments during Japanese Apricot Fruit Development and Ripening

Abstract

Auxin/indole-3-acetic acid (Aux/IAA) is a transcriptional repressor in the auxin signaling pathway that plays a role in several plant growth and development as well as fruit and embryo development. However, it is unclear what role they play in Japanese apricot (Prunus mume) fruit development and maturity. To investigate the role of Aux/IAA genes in fruit texture, development, and maturity, we comprehensively identified and expressed 19 PmIAA genes, and demonstrated their conserved domains and homology across species. The majority of PmIAA genes are highly responsive and expressed in different hormone treatments. PmIAA2, PmIAA5, PmIAA7, PmIAA10, PmIAA13, PmIAA18, and PmIAA19 showed a substantial increase in expression, suggesting that these genes are involved in fruit growth and maturity. During fruit maturation, alteration in the expression of PmIAA genes in response to 1-Methylcyclopropene (1-MCP) treatment revealed an interaction between auxin and ethylene. The current study investigated the response of Aux/IAA development regulators to auxin during fruit ripening, with the goal of better understanding their potential application in functional genomics.

Keywords: Aux/IAA; Japanese apricot; fruit maturity; hormones.

Figure 1

Phylogenetic analysis of PmIAA genes among different family members of Japanese apricot, peach, and Arabidopsis shown in green, red, and blue color dots, respectively. The number on the branches are the bootstrap values and are presented on each node. The outside circle of the phylogenetic tree shows different clades of the tree.

Figure 2

Analysis of phylogeny, gene structure and conserved motif of PmIAAs (A) The phylogenetic relationship of PmIAAs was constructed using MEGA 7.0 (B) conserved motif distribution of PmIAAs. Ten conserved motifs were labeled with different colors using MEME program (C) gene structural organization (CDS, UTR) of PmIAAs. The relative position is uniformly shown based on the Kilobase scale at the bottom of the figures.

Figure 3

Various cis-elements were identified using the PlantCARE database. The different cis-elements biological terms are shown in different colors.

Figure 4

Chromosomal position and gene duplication analysis (A) The chromosomal position of each PmIAA gene was mapped according to the Japanese apricot genome (B) syntenic analysis for gene duplication showed pairs among different chromosomes The gene IDs on the chromosomes indicate the positions of centromeres and the scale on the circle is in Megabases.

Figure 5

Expression of PmIAA genes in response to (A) auxin (B) GA (C) ABA (D) SA treatments was analyzed through qRT-PCR. The expression levels of PmIAA genes in control seedlings were set to a value of 1. The error bar represents the standard error of their biological repeats. Significant differences between control and treated samples are indicated in an asterisk (*). The sign * represents p ≤ 0.05, ** represents p ≤ 0.01 and *** represent p ≤ 0.001.

Figure 6

The expression of PmIAA genes in response to 1-MCP treatment was analyzed through qRT-PCR. The expression levels of PmIAA genes in control seedlings were set to a value of 1. The error bar represents the standard error of their biological repeats. Significant differences between control and treated samples are indicated in asterisk (*). The sign * represents p ≤ 0.05, ** represents p ≤ 0.01 and *** represents p ≤0.001.

Figure 7

Changes in ethylene production (A) and fruit firmness (B). The horizontal axis represents the stages of fruit development. The error bar on data represents the standard error (±) of three individual repeats.

Figure 8

Expression profiles (hierarchical clustering) of PmIAA genes during different stages of fruit development and ripening. Color key shows the expression as red (up-regulated) and green (down-regulated) of the genes. Stages (S1–S6) and the fruit sample are shown under the Heatmap.