Abstract
BackgroundsPomegranate is an excellent tree species with nutritional, medicinal, ornamental and ecological values. Studies have confirmed that SPL factors play an important role in floral transition and flower development.ResultsUsed bioinformatics methods, 15 SPL (SQUAMOSA promoter-binding protein-like) genes were identified and analyzed from the ‘Taishanhong’ pomegranate (P. granatum L.) genome. Phylogenetic analysis showed that PgSPLs were divided into six subfamilies (G1 ~ G6). PgSPL promoter sequences contained multiple cis-acting elements associated with abiotic stress or hormonal response. Based on the transcriptome data, expression profiles of different tissues and different developmental stages showed that PgSPL genes had distinct temporal and spatial expression characteristics. The expression analysis of miR156 in small RNA sequencing results showed that miR156 negatively regulated the expression of target genes. qRT-PCR analysis showed that the expression levels of PgSPL2, PgSPL3, PgSPL6, PgSPL11 and PgSPL14 in leaves were significantly higher than those in buds and stems (p < 0.05). The expression levels of PgSPL5, PgSPL12 and PgSPL13 in flower buds were significantly higher than that in leaves and stems (p < 0.05). The full-length of coding sequence of PgSPL5 and PgSPL13 were obtained by homologous cloning technology. The full length of PgSPL5 is 1020 bp, and PgSPL13 is 489 bp, which encodes 339 and 162 amino acids, respectively. Further investigation revealed that PgSPL5 and PgSPL13 proteins were located in the nucleus. Exogenous plant growth regulator induction experiments showed that PgSPL5 was up-regulated in leaves and stems. PgSPL13 was up-regulated in leaves and down-regulated in stems. When sprayed with 6-BA, IBA and PP333 respectively, PgSPL5 and PgSPL13 were up-regulated most significantly at P2 (bud vertical diameter was 5.1 ~ 12.0 mm) stage of bisexual and functional male flowers.ConclusionsOur findings suggested that PgSPL2, PgSPL3, PgSPL6, PgSPL11 and PgSPL14 played roles in leaves development of pomegranate. PgSPL5, PgSPL12 and PgSPL13 played roles in pomegranate flower development. PgSPL5 and PgSPL13 were involved in the response process of different plant hormone signal transduction in pomegranate development. This study provided a robust basis for further functional analyses of SPL genes in pomegranate.
Highlights
Transcription factors can bind with cis-acting elements of the promoter, which activate or suppress the expression of downstream target genes
Identification and characterization of SQUAMOSA promoter-binding protein-like (SPL) transcription factors Fifteen SPL gene family members were identified from the genome of ‘Taishanhong’ pomegranate
The results showed that PgSPL1, PgSPL2, PgSPL3, PgSPL6, PgSPL7, PgSPL11, PgSPL12, PgSPL13, PgSPL14 and PgSPL15 were potential targets for miR156, and these genes were clustered in G2, G3 and G5 subgroups
Summary
Transcription factors can bind with cis-acting elements of the promoter, which activate or suppress the expression of downstream target genes. The transcription factors involved in floral organ development mainly include MADS-box [1], bHLH [2], YABBY [3] and SPL [4]. The plant-specific SPL (SQUAMOSA promoter binding protein-like) transcription factor is involved in the formation and development of flowers, leaf morphogenesis, and other biological processes [5, 6]. SPL family genes were originally isolated from A. majus [9]. They regulate early flowering of plants by binding with the SQUAMOSA promoter of MADS-box family genes [9]. In Arabidopsis, 17 SPL genes have been isolated and named as SPL1 ~ SPL16. Many researchers have successively identified SPL family genes in other species, such as 28 SPL genes in poplar (Populus trichocarpa) [11], 15 in tomato (Solanum lycopersicum) [12], 19 in rice (O. sativa) [13], 27 in apple (M. domestica Borkh.) [14] and 18 SPL genes in grape (Vitis vinifera L.) [15]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
