The phytohormone abscisic acid (ABA) regulates growth, development, and response to abiotic stress in plants. The core ABA signaling has three key components: ABA receptors PYRABACTIN RESISTANCE 1 and PYR1-Like protein (PYR1/PYLs), type 2C protein phosphatases (PP2Cs) and SNF1- related protein Kinase 2s (SnRK2s). In the presence of ABA, PYR1/PYLs bind to and inhibit PP2Cs, leading to the release of SnRK2s from suppression, to activate downstream events such as ABA-responsive gene expression. To identify new components in the ABA signaling pathway, we performed a yeast two-hybrid screen for PYLs and SnRK2s interactors. We identified two proteins that interact with PYLs and SnRK2s: Ty pe One Protein Phosphatase 1 (TOPP1) and its regulatory protein At Inhibitor 2 (AtI-2). We show that TOPP1 and AtI-2 inhibit SnRK2.6 activity in vitro and that the inhibition is reversed by PYLs in the presence of ABA. Mutants topp1-1topp4-1 and ati-2are hypersensitive to ABA during seed germination. ABA-responsive genes are highly up regulated in topp1-1topp4-1 and ati-2 mutants. Taken together, our results suggest that the TOPP1 and AtI-2 form a complex that negatively modulates ABA signaling by interacting with PYLs and SnRK2s
","abstract_html":"<p>The phytohormone abscisic acid (ABA) regulates growth, development, and response to abiotic stress in plants. The core ABA signaling has three key components: ABA receptors PYRABACTIN RESISTANCE 1 and PYR1-Like protein (PYR1/PYLs), type 2C protein phosphatases (PP2Cs) and SNF1- related protein Kinase 2s (SnRK2s). In the presence of ABA, PYR1/PYLs bind to and inhibit PP2Cs, leading to the release of SnRK2s from suppression, to activate downstream events such as ABA-responsive gene expression. To identify new components in the ABA signaling pathway, we performed a yeast two-hybrid screen for PYLs and SnRK2s interactors. We identified two proteins that interact with PYLs and SnRK2s: Ty pe One Protein Phosphatase 1 (TOPP1) and its regulatory protein At Inhibitor 2 (AtI-2). We show that TOPP1 and AtI-2 inhibit SnRK2.6 activity <em>in vitro</em> and that the inhibition is reversed by PYLs in the presence of ABA. Mutants <em>topp1-1topp4-1 </em>and <em>ati-2</em>are hypersensitive to ABA during seed germination. ABA-responsive genes are highly up regulated in <em>topp1-1topp4-1 </em>and <em>ati-2</em> mutants. Taken together, our results suggest that the TOPP1 and AtI-2 form a complex that negatively modulates ABA signaling by interacting with PYLs and SnRK2s</p>","abstract_has_math":false,"creators":["Hou, Yueh-Ju"],"institution":null,"degree_name":"Doctor of Philosophy (PhD)","degree_level":"Dissertation","degree_discipline":"Horticulture and Landscape Architecture","degree_department":null,"school":null,"contributors":["Jian-Kang Zhu","Paul Michael Hasegawa","David Rhodes","Jin-Rong Xu"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2014,"date_issued":"2014-10-01T07:00:00Z","date_published":"2014-10-01T07:00:00Z","updated_at":"2026-07-24T03:53:28Z","subjects":["Biology","Botany"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://docs.lib.purdue.edu/open_access_dissertations/288","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Jian-Kang Zhu","Paul Michael Hasegawa","David Rhodes","Jin-Rong Xu"]},{"key":"dc:creator","label":"Author","values":["Hou, Yueh-Ju"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"thesis:degree_discipline","label":"Discipline","values":["Horticulture and Landscape Architecture"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Doctor of Philosophy (PhD)"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Biology","Botany"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://docs.lib.purdue.edu/open_access_dissertations/288"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["The phytohormone abscisic acid (ABA) regulates growth, development, and response to abiotic stress in plants. The core ABA signaling has three key components: ABA receptors PYRABACTIN RESISTANCE 1 and PYR1-Like protein (PYR1/PYLs), type 2C protein phosphatases (PP2Cs) and SNF1- related protein Kinase 2s (SnRK2s). In the presence of ABA, PYR1/PYLs bind to and inhibit PP2Cs, leading to the release of SnRK2s from suppression, to activate downstream events such as ABA-responsive gene expression. To identify new components in the ABA signaling pathway, we performed a yeast two-hybrid screen for PYLs and SnRK2s interactors. We identified two proteins that interact with PYLs and SnRK2s: Ty pe One Protein Phosphatase 1 (TOPP1) and its regulatory protein At Inhibitor 2 (AtI-2). We show that TOPP1 and AtI-2 inhibit SnRK2.6 activity in vitro and that the inhibition is reversed by PYLs in the presence of ABA. Mutants topp1-1topp4-1 and ati-2are hypersensitive to ABA during seed germination. ABA-responsive genes are highly up regulated in topp1-1topp4-1 and ati-2 mutants. Taken together, our results suggest that the TOPP1 and AtI-2 form a complex that negatively modulates ABA signaling by interacting with PYLs and SnRK2s
"]},{"key":"dc:title","label":"Title","values":["Identification and characterization of signal components in early ABA signaling in Arabidopsis"]}]}],"canonical_facts":{"dc:contributor":["Jian-Kang Zhu","Paul Michael Hasegawa","David Rhodes","Jin-Rong Xu"],"dc:creator":["Hou, Yueh-Ju"],"dc:description.abstract":["The phytohormone abscisic acid (ABA) regulates growth, development, and response to abiotic stress in plants. The core ABA signaling has three key components: ABA receptors PYRABACTIN RESISTANCE 1 and PYR1-Like protein (PYR1/PYLs), type 2C protein phosphatases (PP2Cs) and SNF1- related protein Kinase 2s (SnRK2s). In the presence of ABA, PYR1/PYLs bind to and inhibit PP2Cs, leading to the release of SnRK2s from suppression, to activate downstream events such as ABA-responsive gene expression. To identify new components in the ABA signaling pathway, we performed a yeast two-hybrid screen for PYLs and SnRK2s interactors. We identified two proteins that interact with PYLs and SnRK2s: Ty pe One Protein Phosphatase 1 (TOPP1) and its regulatory protein At Inhibitor 2 (AtI-2). We show that TOPP1 and AtI-2 inhibit SnRK2.6 activity in vitro and that the inhibition is reversed by PYLs in the presence of ABA. Mutants topp1-1topp4-1 and ati-2are hypersensitive to ABA during seed germination. ABA-responsive genes are highly up regulated in topp1-1topp4-1 and ati-2 mutants. Taken together, our results suggest that the TOPP1 and AtI-2 form a complex that negatively modulates ABA signaling by interacting with PYLs and SnRK2s
"],"dc:identifier":["https://docs.lib.purdue.edu/open_access_dissertations/288"],"dc:subject":["Biology","Botany"],"dc:title":["Identification and characterization of signal components in early ABA signaling in Arabidopsis"],"thesis:degree_discipline":["Horticulture and Landscape Architecture"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Doctor of Philosophy (PhD)"]},"updated_at":"2026-07-24T03:53:28Z"}