title: Molecular Cloning and Characterization of Four Genes Encoding Ethylene Receptors Associated with Pineapple (Ananas comosus L.) Flowering.
abstract: Exogenous ethylene, or ethephon, has been widely used to induce pineapple flowering, but the molecular mechanism behind ethephon induction is still unclear. In this study, we cloned four genes encoding ethylene receptors (designated AcERS1a, AcERS1b, AcETR2a, and AcETR2b). The 5' flanking sequences of these four genes were also cloned by self-formed adaptor PCR and SiteFinding-PCR, and a group of putative cis-acting elements was identified. Phylogenetic tree analysis indicated that AcERS1a, AcERS1b, AcETR2a, and AcETR2b belonged to the plant ERS1s and ETR2/EIN4-like groups. Quantitative real-time PCR showed that AcETR2a and AcETR2b (subfamily 2) were more sensitive to ethylene treatment compared with AcERS1a and AcERS1b (subfamily 1). The relative expression of AcERS1b, AcETR2a, and AcETR2b was significantly increased during the earlier period of pineapple inflorescence formation, especially at 1-9 days after ethylene treatment (DAET), whereas AcERS1a expression changed less than these three genes. In situ hybridization results showed that bract primordia (BP) and flower primordia (FP) appeared at 9 and 21 DAET, respectively, and flowers were formed at 37 DAET. AcERS1a, AcERS1b, AcETR2a, and AcETR2b were mainly expressed in the shoot apex at 1-4 DAET; thereafter, with the appearance of BP and FP, higher expression of these genes was found in these new structures. Finally, at 37 DAET, the expression of these genes was mainly focused in the flower but was also low in other structures. These findings indicate that these four ethylene receptor genes, especially AcERS1b, AcETR2a, and AcETR2b, play important roles during pineapple flowering induced by exogenous ethephon.
authors.affiliation: South Subtropical Crop Research Institute, Chinese Academy of Tropical Agricultural SciencesZhanjiang, China; Key Laboratory of Tropical Fruit Biology, Ministry of AgricultureZhanjiang, China.
authors.forename: Yun-He
authors.initials: YH
authors.lastname: Li
authors.affiliation: South Subtropical Crop Research Institute, Chinese Academy of Tropical Agricultural Sciences Zhanjiang, China.
authors.forename: Qing-Song
authors.initials: QS
authors.lastname: Wu
authors.affiliation: The Key Laboratory of Gene Engineering of the Ministry of Education, School of Life Sciences, Sun Yat-sen University Guangzhou, China.
authors.forename: Xia
authors.initials: X
authors.lastname: Huang
authors.affiliation: South Subtropical Crop Research Institute, Chinese Academy of Tropical Agricultural Sciences Zhanjiang, China.
authors.forename: Sheng-Hui
authors.initials: SH
authors.lastname: Liu
authors.affiliation: South Subtropical Crop Research Institute, Chinese Academy of Tropical Agricultural Sciences Zhanjiang, China.
authors.forename: Hong-Na
authors.initials: HN
authors.lastname: Zhang
authors.affiliation: South Subtropical Crop Research Institute, Chinese Academy of Tropical Agricultural Sciences Zhanjiang, China.
authors.forename: Zhi
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: South Subtropical Crop Research Institute, Chinese Academy of Tropical Agricultural Sciences Zhanjiang, China.
authors.forename: Guang-Ming
authors.initials: GM
authors.lastname: Sun
keywords: Ananas comosus L.; ethylene; ethylene receptors; flowering; inflorescence development