title: Phytochrome interacting factors (PIFs) are essential regulators for sucrose-induced hypocotyl elongation in Arabidopsis.
abstract: Phytochrome interacting factors (PIFs) are members of a subfamily of basic helix-loop-helix transcript factors and have been proposed to act as positive regulators of hypocotyl elongation under normal condition. Here, we show that PIF1, 3, 4, 5 together play a central role in sucrose-induced hypocotyl elongation. When seedlings grown in light were transferred to darkness, exogenously applied sucrose significantly induced hypocotyl elongation in wild type Col-0, but this effect was impaired in all tested pif mutants, especially in the quadruple mutant pif1pif3pif4pif5 (pifq). Subsequent experiments showed that under various light/dark (L/D) cycle conditions sucrose still markedly induced hypocotyl elongation in Col-0, but exhibited little effects in pifq. Phytohormone gibberellins (GAs) have been proven to be required for sucrose-induced hypocotyl elongation, but application of GA(3) (an active form of GAs) was not able to rescue the impairment observed in pifq, suggesting that impairment of sucrose-induced hypocotyl elongation in pifq is not due to the reduced endogenous GAs. Interestingly, through RT-PCR assay, we found that sucrose up-regulated the transcript level of PIF1, 3, 4, 5 in darkness. Furthermore, this effect was dependent on the presence of GAs. Additionally, under continuous light condition, sucrose markedly inhibited the hypocotyl elongation in Col-0 but not in pifq, whereas exogenous GA(3) could recover the repression in Col-0 but only showed slight effect in pifq. These results collectively indicate that PIFs together with GAs control the effect of sucrose on hypocotyl elongation in Arabidopsis seedlings.
authors.affiliation: Key Laboratory of Arid and Grassland Agroecology (Ministry of Education), School of Life Sciences, Lanzhou University, Lanzhou Gansu 730000, People's Republic of China.
authors.forename: Zhongjuan
authors.initials: Z
authors.lastname: Liu
authors.forename: Yongqiang
authors.initials: Y
authors.lastname: Zhang
authors.forename: Rongzhi
authors.initials: R
authors.lastname: Liu
authors.forename: Hualing
authors.initials: H
authors.lastname: Hao
authors.forename: Zhi
authors.initials: Z
authors.lastname: Wang
authors.forename: Yurong
authors.initials: Y
authors.lastname: Bi
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics / Q000502:physiology*; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000502:physiology*; D003624:Darkness; D018506:Gene Expression Regulation, Plant; D005875:Gibberellins / Q000494:pharmacology; D018546:Hypocotyl / Q000254:growth & development* / Q000502:physiology / Q000528:radiation effects; D008027:Light; D009154:Mutation; D017440:Photoperiod; D010834:Phytochrome / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D018749:RNA, Plant / Q000235:genetics; D036226:Seedlings / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D013395:Sucrose / Q000494:pharmacology*
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D005875:Gibberellins; D010834:Phytochrome; D012333:RNA, Messenger; D018749:RNA, Plant; D013395:Sucrose; C508068:At2g20180 protein, Arabidopsis; C116162:PIF3 protein, Arabidopsis; C459466:PIF4 protein, Arabidopsis; C497729:PIF5 protein, Arabidopsis