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<p>Petal senescence is a type of programmed cell death (PCD). Although petal PCD has been reported to occur in mesophyll earlier than in epidermis in several plant species, entire petals have been used in many studies without distinguishing the tissues. We examined the factors potentially responsible for the different PCD progressions in epidermis and mesophyll during inner tepal (homologous to petal) senescence in lily flowers. Cellular collapse, chromatin fragmentation, and DNA fragmentation began in the mesophyll of inner tepals prior to epidermis. After flower opening, sugar content decreased faster in the mesophyll than in epidermis. Proline content increased in the epidermis and mesophyll but largely declined in epidermis before the visual tepal senescence appeared, which was accompanied by an increase in the transcript level of <i>LhProDH</i> encoding proline dehydrogenase. Higher sugar content and active proline catabolism may delay PCD progression in epidermis. The transcript levels of some homologs of NAC transcription factor genes, including <i>LhNAP</i> and <i>LhNAC87</i>, whose Arabidopsis homologs are known to regulate leaf senescence, increased, whereas <i>LhNAC75</i> and <i>LhNAC82</i> decreased during tepal senescence, suggesting that these genes are involved in positive and negative regulation of senescence, respectively. <i>LhNAP</i>, <i>LhNAC87</i>, and PCD-related genes encoding proteases and nucleases were upregulated in the mesophyll prior to epidermis, whereas <i>LhNAC82</i> and Bax inhibitor gene were abundant in epidermis at later stages of tepal senescence. These results provide a detailed characterization of the differences in PCD progression between epidermis and mesophyll during lily tepal senescence and suggest that they are regulated at the molecular level.</p>

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Differential Expression of LhNAC Homologs Between Epidermis and Mesophyll During Tepal Senescence in Lily

  • 期刊论文

  • 发表日期：

    2025年10月14日

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  • Hayato Morimoto,
  • Kenichi Shibuya

摘要

Petal senescence is a type of programmed cell death (PCD). Although petal PCD has been reported to occur in mesophyll earlier than in epidermis in several plant species, entire petals have been used in many studies without distinguishing the tissues. We examined the factors potentially responsible for the different PCD progressions in epidermis and mesophyll during inner tepal (homologous to petal) senescence in lily flowers. Cellular collapse, chromatin fragmentation, and DNA fragmentation began in the mesophyll of inner tepals prior to epidermis. After flower opening, sugar content decreased faster in the mesophyll than in epidermis. Proline content increased in the epidermis and mesophyll but largely declined in epidermis before the visual tepal senescence appeared, which was accompanied by an increase in the transcript level of LhProDH encoding proline dehydrogenase. Higher sugar content and active proline catabolism may delay PCD progression in epidermis. The transcript levels of some homologs of NAC transcription factor genes, including LhNAP and LhNAC87, whose Arabidopsis homologs are known to regulate leaf senescence, increased, whereas LhNAC75 and LhNAC82 decreased during tepal senescence, suggesting that these genes are involved in positive and negative regulation of senescence, respectively. LhNAP, LhNAC87, and PCD-related genes encoding proteases and nucleases were upregulated in the mesophyll prior to epidermis, whereas LhNAC82 and Bax inhibitor gene were abundant in epidermis at later stages of tepal senescence. These results provide a detailed characterization of the differences in PCD progression between epidermis and mesophyll during lily tepal senescence and suggest that they are regulated at the molecular level.