CPPU may induce gibberellin-independent parthenocarpy associated with PbRR9 in 'Dangshansu' pear

• Published in: Horticulture research Vol. 7; no. 1; p. 68
• Main Authors: Cong, Liu, Wu, Ting, Liu, Hanting, Wang, Huibin, Zhang, Haiqi, Zhao, Guangping, Wen, Yao, Shi, Qianrong, Xu, Lingfei, Wang, Zhigang
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 01.05.2020; Nature Publishing Group UK
• Subjects: Abscisic acid; Acetic acid; Biosynthesis; Cell division; Cytokinins; Dioxygenase; Fruit set; Fruits; Gene sequencing; Genes; Gibberellins; Indoleacetic acid; Monooxygenase; Oxidase; Phenylurea; Promoters; Pyrus; Pyruvic acid; Ribonucleic acid; RNA; Tomatoes; Yeasts; Cytokinin; Fruiting
• ISSN: 2662-6810; 2052-7276
• DOI: 10.1038/s41438-020-0285-5

Parthenocarpy is a valuable trait in self-incompatible plants, such as pear. -(2-chloro-4-pyridyl)- -phenylurea (CPPU), a synthetic cytokinin analog, can induce parthenocarpy in pear ( spp.), but the mechanism of induction is unclear. To investigate the role of gibberellin in CPPU-induced parthenocarpy in pear, CPPU supplemented with paclobutrazol (PAC) was sprayed onto 'Dangshansu' pear. We found that the fruit set rate of pear treated with CPPU supplemented with PAC was identical to that in a CPPU-alone treatment group. In regard to cell development, CPPU mainly promoted hypanthium cell division and expansion, and PAC application had no influence on CPPU-induced cell development. RNA sequencing revealed that and genes were not differentially expressed following CPPU treatment. According to the analysis of fruit phytohormone content, the CPPU treatments did not induce gibberellin biosynthesis. These results suggest that CPPU-induced parthenocarpy may be gibberellin independent in 'Dangshansu' pear. After CPPU treatment, the indole acetic acid (IAA) content in fruit was significantly increased, and the abscisic acid (ABA) content was significantly decreased. Similarly, RNA sequencing revealed that many genes involved in the auxin and ABA pathways were significantly differentially expressed in the CPPU treatment groups; among them, ( ) was significantly upregulated and ( ) was significantly downregulated. IAA and ABA may thus play important roles in CPPU-induced parthenocarpy. ( ), , and were then selected to further elucidate the mechanism of CPPU-induced parthenocarpy. A yeast one-hybrid assay indicated that can combine with the and promoters. Dual luciferase assays revealed that can promote and repress the activities of the and promoters, respectively. After the transient expression of in fruits, expression was significantly upregulated, and expression was significantly downregulated. This study uncovered a CPPU-induced parthenocarpy mechanism that is different from that in tomato. CPPU may upregulate and downregulate by upregulating , thereby increasing IAA content and decreasing ABA content to ultimately induce parthenocarpy in 'Dangshansu' pear. However, because only a single time point was used and because 'botanical' and 'accessory' fruits have different structures, this conclusion is still preliminary.