Tree Genetics & Genomes

, 14:61 | Cite as

Genome-wide analysis and identification of the SMXL gene family in apple (Malus × domestica)

  • Rui Li
  • Jian-Ping An
  • Chun-Xiang You
  • Xiao-Fei WangEmail author
  • Yu-Jin HaoEmail author
Original Article
Part of the following topical collections:
  1. Genome Biology


Strigolactones (SLs) are a recently discovered type of plant hormone that controls various developmental processes. The DWARF53 (D53) protein in rice and the SMAX1-LIKE (SMXL) family in Arabidopsis repress SL signaling. In this study, bioinformatics analyses were performed, and 236 SMXL proteins were identified in 28 sequenced plants. A phylogenetic analysis indicated that all potential SMXL proteins could be divided into three groups and that the SMXL proteins may have originated in Bryophytes. An analysis of the SMXL chromosomal locations suggested that gene duplication events at different times led to expansion of the SMXL family members in Angiospermae. Subsequently, the gene structure and protein modeling of MdSMXLs showed that they are highly conserved. The expression patterns of MdSMXLs indicated that they were expressed in different organs of apple (stems, roots, leaves, flowers, and fruits) at varying levels and that MdSMXLs may participate in the SL signaling pathway and the response to abiotic stress. This study provides a valuable foundation for additional investigations into the function of the SMXL gene family in plants.


Strigolactones SMXL gene family Genome-wide identification Expression analysis Apple 


Funding information

This work was supported by grants from the National Natural Science Foundation of China (31601742, U1706202), the Ministry of Agriculture of China (CARS-28), Shandong Province (SDAIT-06-03), and the Ministry of Education of China (IRT15R42).

Supplementary material

11295_2018_1275_MOESM1_ESM.doc (34 kb)
Supplementary Table 1 Primers used for quantitative real-time PCR of the SMXL genes in apple. (DOC 34 kb)
11295_2018_1275_MOESM2_ESM.jpg (598 kb)
Supplementary Figure S1 Phylogenetic relationships between Arabidopsis and apple SMXL proteins calculated using the neighbor-joining (NJ) method. A total of 1000 bootstrapping replicates was calculated for each node. The proteins were classified into three distinct subgroups (classes I, II, and III), which are distinguished by their background color. The distance (indicated by ‘0.05’) is the percent sequence divergence. (JPG 597 kb)
11295_2018_1275_MOESM3_ESM.jpg (682 kb)
Supplementary Figure S2 Phylogenetic relationships between Arabidopsis and apple SMXL proteins calculated using the maximum likelihood (ML) method. The proteins were classified into three distinct subgroups (classes I, II, and III), which are marked by a colored background. The distance (indicated by ‘0.2’) is the percent sequence divergence. (JPG 682 kb)
11295_2018_1275_MOESM4_ESM.jpg (744 kb)
Supplementary Figure S3 Exon/intron structure of SMXL/D53 genes in Arabidopsis and Oryza sativa. Introns and exons are represented by shrunken lines and red boxes, respectively. The length in base pairs is indicated for each intron and exon. (JPG 743 kb)
11295_2018_1275_MOESM5_ESM.jpg (3.8 mb)
Supplementary Figure S4 Sequence alignment of the conserved domains of the SMXL proteins in apple. (JPG 3876 kb)
11295_2018_1275_MOESM6_ESM.jpg (2.1 mb)
Supplementary Figure S5 Three-dimensional structure analysis of the SMXLs. A, The three-dimensional structure of the ClpB protein. B, The confidence and coverage of the amino acid sequence of MdSMXLs compared to ClpB. (JPG 2195 kb)
11295_2018_1275_MOESM7_ESM.jpg (1.7 mb)
Supplementary Figure S6 MdSMXL expression in response to different abiotic stressors. Expression patterns of MdSMXLs under drought, ABA, salt, and temperature (4 °C) stress. HemI (Version1.0) was used to draw the heatmaps. The color scale representing the relative signal values is shown above. (JPG 1720 kb)
11295_2018_1275_MOESM8_ESM.jpg (6.9 mb)
Supplementary Figure S7 Arabidopsis microarray data showing the response of SMXLs to abiotic stress. (JPG 7024 kb)


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.National Key Laboratory of Crop Biology, National Research Center for Apple Engineering and Technology/College of Horticulture Science and EngineeringShandong Agricultural UniversityTai’anPeople’s Republic of China

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