Light differentially regulates the expression of two members of the auxin-induced 1-aminocyclopropane-1-carboxylate synthase gene family in mung bean (Vigna radiata L.) seedlings.
Auxin induces the expression of the two ethylene-biosynthetic genes VR-ACS6 and VR-ACS7 in etiolated mung bean hypocotyls. However, while it also enhances VR-ACS6 expression in light-grown tissues, it does not up-regulate VR-ACS7 expression in these tissues. Here we show that transfer of 3-day-old etiolated seedlings into light quickly reduced the auxin-induced expression of both genes. However, while auxin-induced VR-ACS6 expression recovered after 24 h of light, VR-ACS7 transcription continued to reduce and was almost completely absent at 36 h. Thus, light differentially modulates the expression of the auxin-inducible VR-ACS genes. In hormone-treated etiolated seedlings, VR-ACS7 was primarily induced in the rapidly elongating zones of hypocotyl and epicotyl tissues, while auxin-induced VR-ACS6 mRNA was evenly distributed throughout the whole seedling. VR-ACS7 promoter-driven beta-glucuronidase (GUS) activity in auxin-treated etiolated transgenic Arabidopsis seedlings was observed in the highly elongating zones of the hypocotyl. During de-etiolation, the GUS activity gradually declined to become confined to the uppermost region of hypocotyls. In situ mRNA localization studies showed that in etiolated mung bean hypocotyls, the auxin-dependent VR-ACS7 transcript was predominantly present in the epidermis, which is the driving site for auxin-mediated elongation. Thus, it appears that the modulation by light of auxin-induced VR-ACS7 expression may correlate closely with the elongation growth response in early seedling development.
Joo
Sunjoo
S
Department of Biology, College of Science, Yonsei University, 120-749 Seoul, Korea.
Park
Ky Young
KY
Kim
Woo Taek
WT
D017360:Arabidopsis / Q000235:genetics; D007887:Fabaceae / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D018546:Hypocotyl / Q000201:enzymology / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism*; D008027:Light; D008190:Lyases / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified; D036226:Seedlings / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D014158:Transcription, Genetic
D007210:Indoleacetic Acids; D008190:Lyases; C021773:1-aminocyclopropanecarboxylate synthase