Genome-wide identification and characterization of AINTEGUMENTA-LIKE (AIL) family genes in apple (Malus domestica Borkh.)

MdAIL5 overexpression promotes apple adventitious shoot regeneration by regulating hormone signaling and activating the expression of shoot development-related genes

Adventitious shoot (AS) regeneration is a significant factor in the genetic transformation of horticultural plants. It is also a noteworthy approach to their vegetative propagation. AS regeneration remains highly dependent on the genotype or maturity of explants. We here found that the AS regeneration abilities of apple leaves were positively correlated with MdAIL5 expression. MdAIL5 overexpression dramatically increased AS regeneration efficiency. Notably, MdAIL5 overexpression could restore the AS formation ability of explants to a certain extent, which was lost with an increase in maturity. Endogenous hormone detection revealed that MdAIL5 overexpression changed the contents of auxin, cytokinin (CK), and other hormones in apple leaves. Transcriptome analysis revealed that many genes related to auxin, CK, and brassinolide signaling pathways were significantly and differentially expressed between MdAIL5-overexpressing transgenic apple and wild-type apple plants. Yeast one-hybrid assays, the electrophoretic mobility shift assay, and the dual-luciferase reporter assay revealed that MdAIL5 directly binds to MdARF9 and MdHB14 promoters and positively affects their expression. We here established a model of MdAIL5 regulating AS formation, which acts as a theoretical basis for facilitating genotype- or explant maturity-independent AS regeneration in the future.

Genome-wide analysis of MdPLATZ genes and their expression during axillary bud outgrowth in apple (Malus domestica Borkh.)

BACKGROUND

Branching is a plastic character that affects plant architecture and spatial structure. The trait is controlled by a variety of plant hormones through coordination with environmental signals. Plant AT-rich sequence and zinc-binding protein (PLATZ) is a transcription factor that plays an important role in plant growth and development. However, systematic research on the role of the PLATZ family in apple branching has not been conducted previously.

RESULTS

In this study, a total of 17 PLATZ genes were identified and characterized from the apple genome. The 83 PLATZ proteins from apple, tomato, Arabidopsis, rice, and maize were classified into three groups based on the topological structure of the phylogenetic tree. The phylogenetic relationships, conserved motifs, gene structure, regulatory cis-acting elements, and microRNAs of the MdPLATZ family members were predicted. Expression analysis revealed that MdPLATZ genes exhibited distinct expression patterns in different tissues. The expression patterns of the MdPLATZ genes were systematically investigated in response to treatments that impact apple branching [thidazuron (TDZ) and decapitation]. The expression of MdPLATZ1, 6, 7, 8, 9, 15, and 16 was regulated during axillary bud outgrowth based on RNA-sequencing data obtained from apple axillary buds treated by decapitation or exogenous TDZ application. Quantitative real-time PCR analysis showed that MdPLATZ6 was strongly downregulated in response to the TDZ and decapitation treatments, however, MdPLATZ15 was significantly upregulated in response to TDZ, but exhibited little response to decapitation. Furthermore, the co-expression network showed that PLATZ might be involved in shoot branching by regulating branching-related genes or mediating cytokinin or auxin pathway.

CONCLUSION

The results provide valuable information for further functional investigation of MdPLATZ genes in the control of axillary bud outgrowth in apple.

Genome-wide characterization of AINTEGUMENTA-LIKE family in Medicago truncatula reveals the significant roles of AINTEGUMENTAs in leaf growth

AINTEGUMENTA-LIKE (AIL) transcription factors are widely studied and play crucial roles in plant growth and development. However, the functions of the AIL family in legume species are largely unknown. In this study, 11 MtAIL genes were identified in the model legume Medicago truncatula, of which four of them are MtANTs. In situ analysis showed that MtANT1 was highly expressed in the shoot apical meristem (SAM) and leaf primordium. Characterization of mtant1 mtant2 mtant3 mtant4 quadruple mutants and MtANT1-overexpressing plants revealed that MtANTs were not only necessary but also sufficient for the regulation of leaf size, and indicated that they mainly function in the regulation of cell proliferation during secondary morphogenesis of leaves in M. truncatula. This study systematically analyzed the MtAIL family at the genome-wide level and revealed the functions of MtANTs in leaf growth. Thus, these genes may provide a potential application for promoting the biomass of legume forages.