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1.
J Exp Bot ; 72(10): 3647-3660, 2021 05 04.
Artigo em Inglês | MEDLINE | ID: mdl-33619529

RESUMO

During secondary growth, the thickening of plant organs, wood (xylem) and bast (phloem) is continuously produced by the vascular cambium. In Arabidopsis hypocotyl and root, we can distinguish two phases of secondary growth based on cell morphology and production rate. The first phase, in which xylem and phloem are equally produced, precedes the xylem expansion phase in which xylem formation is enhanced and xylem fibers differentiate. It is known that gibberellins (GA) trigger this developmental transition via degradation of DELLA proteins and that the cambium master regulator BREVIPEDICELLUS/KNAT1 (BP/KNAT1) and receptor like kinases ERECTA and ERL1 regulate this process downstream of GA. However, our understanding of the regulatory network underlying GA-mediated secondary growth is still limited. Here, we demonstrate that DELLA-mediated xylem expansion in Arabidopsis hypocotyl is mainly achieved through DELLA family members RGA and GAI, which promote cambium senescence. We further show that AUXIN RESPONSE FACTOR 6 (ARF6) and ARF8, which physically interact with DELLAs, specifically repress phloem proliferation and induce cambium senescence during the xylem expansion phase. Moreover, the inactivation of BP in arf6 arf8 background revealed an essential role for ARF6 and ARF8 in cambium establishment and maintenance. Overall, our results shed light on a pivotal hormone cross-talk between GA and auxin in the context of plant secondary growth.


Assuntos
Arabidopsis/crescimento & desenvolvimento , Câmbio/crescimento & desenvolvimento , Giberelinas , Hipocótilo , Ácidos Indolacéticos , Proteínas de Arabidopsis , Homeostase , Hipocótilo/crescimento & desenvolvimento , Xilema/crescimento & desenvolvimento
2.
J Exp Bot ; 68(1): 89-95, 2017 01.
Artigo em Inglês | MEDLINE | ID: mdl-27965365

RESUMO

Secondary growth occurs in dicotyledons and gymnosperms, and results in an increased girth of plant organs. It is driven primarily by the vascular cambium, which produces thousands of cells throughout the life of several plant species. For instance, even in the small herbaceous model plant Arabidopsis, manual quantification of this massive process is impractical. Here, we provide a comprehensive overview of current methods used to measure radial growth. We discuss the issues and problematics related to its quantification. We highlight recent advances and tools developed for automated cellular phenotyping and its future applications.


Assuntos
Desenvolvimento Vegetal , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/fisiologia , Botânica/métodos , Câmbio/citologia , Câmbio/crescimento & desenvolvimento , Câmbio/fisiologia , Desenvolvimento Vegetal/fisiologia
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