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Expansins, which are important components of plant cell walls, act as loosening factors to directly induce turgor-driven cell wall expansion, regulate the growth and development of roots, leaves, fruits, and other plant organs, and function essentially under environmental stresses. In multiple species, many expansin genes (EXPs) have been cloned and functionally validated but little is known in pomegranate. In this study, a total of 33 PgEXPs were screened from the whole genome data of 'Taishanhong' pomegranate, belonging to the EXPA(25), EXPB(5), EXLA(1), and EXLB(2) subfamilies. Subsequently, the composition and characteristics were analyzed. Members of the same branch shared similar motif compositions and gene structures, implying they had similar biological functions. According to cis-acting element analysis, PgEXPs contained many light and hormone response elements in promoter regions. Analysis of RNA-seq data and protein interaction network indicated that PgEXP26 had relatively higher transcription levels in all pomegranate tissues and might be involved in pectin lyase protein synthesis, whilst PgEXP5 and PgEXP31 might be involved in the production of enzymes associated with cell wall formation. Quantitative real-time PCR (qRT-PCR) results revealed that PgEXP expression levels in fruit peels varied considerably across fruit developmental phases. PgEXP23 was expressed highly in the later stages of fruit development, suggesting that PgEXP23 was essential in fruit ripening. On the other hand, the PgEXP28 expression level was minimal or non-detected. Our work laid a foundation for further investigation into pomegranate expansin gene functions. [ABSTRACT FROM AUTHOR]

Pomegranates (Punica granatum L.) are one of the most fashionable fruits and can be cultivated in both tropical and subtropical regions of the world. It is a shiny and attractive pome due to its cultivation. It belongs to the Lythraceae family. In this study, we analyzed the chloroplast genome of wild pomegranate based on whole genome shotgun sequences. In wild pomegranate, we found 158,645 bp in size, 132 genes containing 84 protein genes, 37 tRNA genes, 8 rRNA genes, and 36.92% of GC content, one infA and two duplicated ycf15 pseudogenes. Moreover, 21 chloroplast genes contained intros that are detected in a large single copy (LSC), small single copy (SSC), and two inverted repeats (IRA and IRB) regions, 17 of which were involved in single introns, while four genes (ycf3, rps12, clpP and rsp12) located in LSC, IRA, and IRB region. In total, 26,272 codons are found in protein-coding genes (PCGs); relative synonymous codon usage (RSCU) analysis revealed that the most abundant amino acid is leucine containing 2773 codons (10.55%), less abundant is methionine amino acid containing 1 codon (0.0032) in the PCGs. Furthermore, a total of 233 cpSSRs were identified in the wild pomegranate cp genome, and their distribution was analyzed in three regions, namely IR, LSC, and SSC. However, 155 cpSSR were found in the LSC (66.5%), followed by 40 cpSSR in the SSC (17.2%) and 38 cpSSR in the IR (16.3%) regions. Phylogenetic validation revealed that wild pomegranate is close to the pemphis acidula species. We believe that the cp genome allocates significant information promising for breeding research of wild pomegranate to Lythraceae. [ABSTRACT FROM AUTHOR]

Pomegranate (Punica granatum) flowers are classified as bisexual flowers and functional male flowers. Functional male flowers have sterile pistils that show abnormal ovule development. In previous studies, we identified INNER NO OUTER (INO), CRABS CLAW (CRC), and BELL1 (BEL1), which were specifically expressed in bisexual and functional male flowers. However, the functions of ovule identity genes and the mechanism underlying ovule sterility in pomegranate remain unknown. Here, we found that the integument primordia formed and then ceased developing in the ovules of functional male flowers with a vertical diameter of 8.1-13.0 mm. Megaspore mother cells were observed in bisexual flowers when the vertical diameters of flowers were 10.1-13.0 mm, but not in functional male flowers. We analyzed the expression patterns of ovule-related genes in pomegranate ovule sterility and found that PgCRC mRNA was highly expressed at a critical stage of ovule development in bisexual flowers. Ectopic expression of PgCRC and PgINO was sufficient to increase seed number in transgenic lines. PgCRC partially complemented the Arabidopsis (Arabidopsis thaliana) crc mutant, and PgINO successfully rescued the seeds set in the Arabidopsis ino mutant. The results of yeast two-hybrid assays, bimolecular fluorescence complementation assays, and genetic data analyses showed that PgCRC and PgINO directly interact with PgBEL1. Our results also showed that PgCRC and PgINO could not interact directly with MADS-box proteins and that PgBEL1 interacted with SEPALLATA proteins. We report the function of PgCRC and PgINO in ovule and seed development and show that PgCRC and PgINO interact with PgBEL1. Thus, our results provide understanding of the genetic regulatory networks underlying ovule development in pomegranate., Competing Interests: Conflict of interest statement. None declared., (© The Author(s) 2022. Published by Oxford University Press on behalf of American Society of Plant Biologists.)