Aug 2026· Plant Science· Vol 372, pp.
113377
· 0 citations· 38 references
Medicine
TL;DR
This study provides new insights into the role of cytokinin metabolism in fruit development and highlights regulatory variation in MdCKX6 as a potential target for apple breeding.
Abstract
Fruit size is a key determinant of apple fruit quality and market value and is strongly influenced by phytohormone-regulated cell proliferation and expansion during early fruit development. Cytokinin oxidase/dehydrogenase (CKX) enzymes regulate cytokinin homeostasis by irreversibly degrading active cytokinins, but the contribution of natural variation in CKX genes to fruit size remains poorly understood. Here, we identified MdCKX6 as a candidate regulator of fruit growth in apple (Malus domestica). MdCKX6 exhibited pronounced allele-specific expression during fruit development in the cultivar 'Royal Gala'. Sequence analysis identified a promoter SNP associated with differential promoter activity and allele-specific expression. Genotyping of diverse apple cultivars and wild Malus accessions revealed a significant association between MdCKX6 promoter genotype and fruit size. Cultivars carrying low-expression alleles produced larger fruits, whereas high-expression alleles were associated with smaller fruits. To investigate gene function, MdCKX6 was overexpressed in tomato, resulting in reduced fruit size. Histological analyses of the transgenic tomato fruit revealed smaller pericarp cells. Transcriptome analysis of transgenic fruits revealed widespread changes in genes associated with cell-cycle regulation, cell wall modification, hormone-related processes, and transcriptional regulation. Together, these results identify MdCKX6 as a potential negative regulator of apple fruit growth and reveal an association between cis-regulatory variants, gene expression, and fruit size. This study provides new insights into the role of cytokinin metabolism in fruit development and highlights regulatory variation in MdCKX6 as a potential target for apple breeding.
The MADS-box gene family comprises key transcription factors that regulate plant growth and development, particularly flower and fruit morphogenesis. However, the evolutionary characteristics of this gene family in sweet orange (
Citrus sinensis
) and their specific regulatory roles in secondary fruit development remain unclear. This study aimed to systematically investigate these aspects by comparing cultivars with distinct fruit phenotypes.
Newhall navel orange (
C. sinensis
‘Newhall’), which exhibits a typical secondary fruit phenotype, and Hamlin sweet orange (
C. sinensis
‘Hamlin’), which lacks this trait, were used as experimental materials. A high-quality, chromosome-level
de novo
genome assembly was generated for Hamlin sweet orange. Comparative genomic analysis was performed to identify drivers of divergence between the two cultivars. Additionally, transcriptomic sequencing was conducted across bud, full bloom, and post-bloom stages, followed by weighted gene co-expression network analysis (WGCNA) to identify gene modules associated with secondary fruit development.
The Hamlin sweet orange genome assembly achieved an N50 of 32.89 Mb. Comparative genomics revealed that tandem duplication is a primary driver of divergence between the two cultivars. Gene family identification showed that Newhall possesses more MADS-box genes (139) than Hamlin (119). Transcriptomic and WGCNA analyses identified gene modules significantly correlated with secondary fruit development, pinpointing CSN
SEP
3 and CSN
AG
6 as key candidate regulatory genes.
This study provides a high-quality reference genome for Hamlin sweet orange and offers valuable transcriptomic insights into the role of MADS-box genes in citrus differentiation and fruit morphogenesis. The identification of CSN
SEP
3 and CSN
AG
6 as critical regulators of secondary fruit development lays a theoretical foundation for molecular breeding programs targeting fruit morphology in citrus.
Jia-Xing Wan, Zhuo-Zhuo Wu, Yan-Ji Yao et al.· Frontiers in Plant Science· 0 citations
This study uncovers a rare case in which a deletion of just two amino acids is sufficient to generate a potent dominant-negative regulator, designated SmMYB1alf-D, which enables reliable prediction of fruit color and provides a breeding strategy to precisely manipulate anthocyanin metabolism.
Yan Li, Yiwen Tian, Wanyue Li et al.· Plant Communications· 0 citations
This review systematically summarizes recent advances in FSP research and highlights the major challenges limiting the application of FSPs, including the relatively weak transcriptional activity of natural promoters, insufficient tissue specificity, and limited cross-species applicability.
Jinzhu Fan, Xin-Yi Tang, Ao-Xue Wang et al.· Plants· 0 citations
expression analysis revealed that WRKY-S is highly expressed during early fruit stages, and CRISPR/Cas9-mediated knockout of WRKY-S produced rounded fruits with reduced cell number along the proximal-distal axis, while overexpression resulted in irregular fruit shapes.
Chunying Feng, Xinshuang Zhang, Ruoyu Yang et al.· Horticulture Research· 0 citations
A systems-level view of blueberry fruit development is provided, highlighting coordinated transcriptional changes across multiple biological pathways during ripening and the identification of conserved gene expression patterns and key regulatory candidates offers valuable targets for improving fruit quality and health-promoting traits in blueberry.
Nayla Zalzalah, Mohamad Elian, Julia C Wozny et al.· BMC Plant Biology· 0 citations
Fruit length is an important fruit quality which greatly influences the preference of consumers, but the underlying genetic mechanism regulating the fruit length in cucumber remains not very clear. In this study, the candidate gene CsSUN about the major QTL FS1.1 was cloned based on the near-isogenic lines (NILs) sun161 and SUN162. CsSUN had a 161 bp deletion in the first exon, giving rise to frameshift mutation and translation termination in the round-shape fruit of cucumber lines. The fruit length reduced by 38% to 46% when CsSUN was knocked out using CRISPR/Cas9 method in cucumber. It is found that the calcium ion levels in sun161 fruits were significantly 15.2% higher than those in SUN162. The calmodulin gene CsCaM11 was highly negatively correlated with fruit length through the regulatory networks involving the fruit length development of the NILs. To identify the function of CsCaM11, the yeast two-hybrid was carried out and it was found that CsCaM11 interacted with CsSUN, and the fruit length reduced by 5.0% to 7.5% compared with WT when CsCaM11 was overexpressed in cucumber, while the fruit length increased by 17.9% compared with WT when Cscam11 was knocked out. Further double-mutant cam11sun phenotypic analysis and subcellular co-localization of the two genes were performed, which revealed that CsCaM11 was epistatic to CsSUN, and that the interaction between them altered the subcellular distribution of CsCaM11. A model was established and elucidated that CsSUN positively regulated the fruit elongation, and CsCaM11 suppressed the fruit elongation by interacting with CsSUN protein.
Tingting Zhang, Ni Han, Peng-Fei Li et al.· Plant Physiology· 0 citations
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