Kir, Gokhan;
Ye, Huaxun;
Nelissen, Hilde;
Neelakandan, Anjanasree K.;
Kusnandar, Andree S.;
Luo, Anding;
Inzé, Dirk;
Sylvester, Anne W.;
Yin, Yanhai;
Becraft, Philip W.
RNA Interference Knockdown of BRASSINOSTEROID INSENSITIVE1 in Maize Reveals Novel Functions for Brassinosteroid Signaling in Controlling Plant Architecture
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Media type:
E-Article
Title:
RNA Interference Knockdown of BRASSINOSTEROID INSENSITIVE1 in Maize Reveals Novel Functions for Brassinosteroid Signaling in Controlling Plant Architecture
Contributor:
Kir, Gokhan;
Ye, Huaxun;
Nelissen, Hilde;
Neelakandan, Anjanasree K.;
Kusnandar, Andree S.;
Luo, Anding;
Inzé, Dirk;
Sylvester, Anne W.;
Yin, Yanhai;
Becraft, Philip W.
imprint:
American Society of Plant Biologists, 2015
Description:
<p>Brassinosteroids (BRs) are plant hormones involved in various growth and developmental processes. The BR signaling system is well established in Arabidopsis (<italic>Arabidopsis thaliana</italic>) and rice (<italic>Oryza sativa</italic>) but poorly understood in maize (<italic>Zea mays</italic>). BRASSINOSTEROID INSENSITIVE1 (BRI1) is a BR receptor, and database searches and additional genomic sequencing identified five maize homologs including duplicate copies of BRI1 itself. RNA interference (RNAi) using the extracellular coding region of a maize<italic>zmbri1</italic>complementary DNA knocked down the expression of all five homologs. Decreased response to exogenously applied brassinolide and altered BR marker gene expression demonstrate that<italic>zmbri1</italic>-RNAi transgenic lines have compromised BR signaling.<italic>zmbri1</italic>-RNAi plants showed dwarf stature due to shortened internodes, with upper internodes most strongly affected. Leaves of<italic>zmbri1</italic>-RNAi plants are dark green, upright, and twisted, with decreased auricle formation. Kinematic analysis showed that decreased cell division and cell elongation both contributed to the shortened leaves. A BRASSINOSTEROID INSENSITIVE1-ETHYL METHANESULFONATE-SUPPRESSOR1-yellow fluorescent protein (BES1-YFP) transgenic line was developed that showed BR-inducible BES1-YFP accumulation in the nucleus, which was decreased in<italic>zmbri1</italic>-RNAi. Expression of the BES1-YFP reporter was strong in the auricle region of developing leaves, suggesting that localized BR signaling is involved in promoting auricle development, consistent with the<italic>zmbri1</italic>-RNAi phenotype. The blade-sheath boundary disruption, shorter ligule, and disrupted auricle morphology of RNAi lines resemble KNOTTED1-LIKE HOMEOBOX (KNOX) mutants, consistent with a mechanistic connection between KNOX genes and BR signaling.</p>