title: Identification and characterization of transcription factors regulating Arabidopsis HAK5.
abstract: Potassium (K) is an essential macronutrient for plant growth and reproduction. HAK5, an Arabidopsis high-affinity K transporter gene, plays an important role in K uptake. Its expression is up-regulated in response to K deprivation and is rapidly down-regulated when sufficient K levels have been re-established. To identify transcription factors regulating HAK5, an Arabidopsis TF FOX (Transcription Factor Full-length cDNA Over-eXpressor) library containing approximately 800 transcription factors was used to transform lines previously transformed with a luciferase reporter gene whose expression was driven by the HAK5 promoter. When grown under sufficient K levels, 87 lines with high luciferase activity were identified, and endogenous HAK5 expression was confirmed in 27 lines. Four lines overexpressing DDF2 (Dwarf and Delayed Flowering 2), JLO (Jagged Lateral Organs), TFII_A (Transcription initiation Factor II_A gamma chain) and bHLH121 (basic Helix-Loop-Helix 121) were chosen for further characterization by luciferase activity, endogenous HAK5 level and root growth in K-deficient conditions. Further analysis showed that the expression of these transcription factors increased in response to low K and salt stress. In comparison with controls, root growth under low K conditions was better in each of these four TF FOX lines. Activation of HAK5 expression by these four transcription factors required at least 310 bp of upstream sequence of the HAK5 promoter. These results indicate that at least these four transcription factors can bind to the HAK5 promoter in response to K limitation and activate HAK5 expression, thus allowing plants to adapt to nutrient stress.
authors.affiliation: RIKEN Center for Sustainable Resource Science, Yokohama, Kanagawa, 230-0045 Japan.
authors.forename: Jong-Pil
authors.initials: JP
authors.lastname: Hong
authors.forename: Yoshizumi
authors.initials: Y
authors.lastname: Takeshi
authors.forename: Youichi
authors.initials: Y
authors.lastname: Kondou
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Schachtman
authors.forename: Minami
authors.initials: M
authors.lastname: Matsui
authors.forename: Ryoung
authors.initials: R
authors.lastname: Shin
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000235:genetics; D005966:Glucuronidase / Q000235:genetics / Q000378:metabolism; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D011188:Potassium / Q000494:pharmacology; D027961:Potassium-Hydrogen Antiporters; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012965:Sodium Chloride / Q000494:pharmacology; D027981:Symporters / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D019473:Transcription Factors, TFII / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D005966:Glucuronidase; D008156:Luciferases; D011188:Potassium; D027961:Potassium-Hydrogen Antiporters; D012097:Repressor Proteins; D012965:Sodium Chloride; D027981:Symporters; D014157:Transcription Factors; D019473:Transcription Factors, TFII; C487099:DDF2 protein, Arabidopsis; C523444:JAGGED LATERAL ORGANS protein, Arabidopsis; C587582:bHLH121 protein, Arabidopsis; C501258:potassium transporter, Arabidopsis; C587583:transcription initiation factor IIA subunit 2, Arabidopsis
keywords: Arabidopsis TFs FOX; HAK5; Potassium-deficient signaling