Abstract
BackgroundApple (Malus domestica Borkh.) is a popular cultivated fruit crop with high economic value in China. Apple floral transition is an important process but liable to be affected by various environmental factors. The 14–3-3 proteins are involved in regulating diverse biological processes in plants, and some 14–3-3 members play vital roles in flowering. However, little information was available about the 14–3-3 members in apple.ResultsIn the current study, we identified eighteen 14–3-3 gene family members from the apple genome database, designated MdGF14a to MdGF14r. The isoforms possess a conserved core region comprising nine antiparallel α-helices and divergent N and C termini. According to their structural and phylogenetic features, Md14–3-3 proteins could be classified into two major evolutionary branches, the epsilon (ɛ) group and the non-epsilon (non-ɛ) group. Moreover, expression profiles derived from transcriptome data and quantitative real-time reverse transcription PCR analysis showed diverse expression patterns of Md14–3-3 genes in various tissues and in response to different sugars and hormone treatments during the floral transition phase. Four Md14–3-3 isoforms (MdGF14a, MdGF14d, MdGF14i, and MdGF14j) exhibiting prominent transcriptional responses to sugars and hormones were selected for further investigation. Furthermore, yeast two-hybrid and bimolecular fluorescence complementation experiments showed that the four Md14–3-3 proteins interact with key floral integrators, MdTFL1 (TERMINAL FLOWER1) and MdFT (FLOWERING LOCUS T). Subcellular localization of four selected Md14–3-3 proteins demonstrated their localization in both the cytoplasm and nucleus.ConclusionWe identified the Md14–3-3 s family in apple comprehensively. Certain Md14–3-3 genes are expressed predominantly during the apple floral transition stage, and may participate in the regulation of flowering through association with flower control genes. Our results provide a preliminary framework for further investigation into the roles of Md14–3-3 s in floral transition.
Highlights
Apple (Malus domestica Borkh.) is a popular cultivated fruit crop with high economic value in China
Genome-wide identification and chromosomal locations of 14–3-3 genes in the apple genome To identify 14–3-3 family members in apple, previously published 15 Arabidopsis 14–3-3 protein sequences were used as queries against the Apple Genome Database using the BLASTp program (E-value
Md14–3-3 s can interact with MdTFL1, and MdFT To address how Md14–3-3 s participate in floral transition, we focused on the floral pathway integrators, TERM INAL FLOWER1 (TFL1) and FLOWERING LOCUS T (FT)
Summary
Apple (Malus domestica Borkh.) is a popular cultivated fruit crop with high economic value in China. The 14–3-3 family, consisting of multiple subunits, is present in all eukaryotic organisms, such as yeast [1], humans [2], and Arabidopsis [3]. They were identified as essential components of the protein/G box complex in Arabidopsis and were named as “G box factor 14-3-3,” or “GF14” [4]. 14–3-3 s usually exist in the form of homodimers or heterodimers [5]; each subunit is able to bind a separate phosphorylated target protein by the recognized binding motifs, namely mode I (RXX (pS/pT) XP or modified motif LX(R/K) SX (pS/pT)XP), and mode II (RX(F/Y) X (pS)XP) [6, 7]. A recent study reported that the phosphorylated transcription factor PHYTOCHROME-INTERA CTING FACTOR 7 (PIF7) can be sequestered in the cytoplasm by 14–3-3 proteins [12]
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