MaBZR1/2 act as transcriptional repressors of ethylene biosynthetic genes in banana fruit

Abstract

Banana fruit (Musa acuminate L.) ripening is a complex genetical process affected by multiple phytohormones and expression of various genes. However, whether plant hormone brassinosteroid (BR) is involved in this process remains obscure. In this work, three genes that encode BR core signaling components brassinazole resistant (BZR) proteins, namely MaBZR1 to MaBZR3, were characterized from banana fruit. MaBZR1-MaBZR3 exhibited both nuclear and cytoplasmic localization and behaved as transcription inhibitors. Expression analysis showed that MaBZR1/2/3 were continuously decreased as fruit ripening proceeded, indicating their negative roles in banana ripening. Moreover, gel shift and transient expression assays demonstrated that MaBZR1/2 could suppress the transcription of ethylene biosynthetic genes, including MaACS1, MaACO13 and MaACO14, which increased gradually during the banana ripening, via specifically binding to CGTGT/CG sequence in their promoters. Importantly, exogenous application of BRs promotes banana ripening, which is presumably due to the accelerated expression of MaACS1 and MaACO13/14, and consequently the ethylene production. Our study indicates that MaBZR1/2 act as transcriptional repressors of ethylene biosynthetic genes during banana fruit ripening.

Brassinosteroids, the Sixth Class of Phytohormones: A Molecular View from the Discovery to Hormonal Interactions in Plant Development and Stress Adaptation

“…Moreover, MaBZR1 and MaBZR2 are capable of suppressing the transcription of these three ethylene biosynthetic genes, which is increased during the fruit ripening process. Additionally, the exogenous application of BR promotes banana fruit ripening due to the acceleration of MaACS1 , MaACO13 , and MaACO14 expression, and consequently, ethylene production occurs, confirming the action of BZR proteins as transcriptional repressors of ethylene biosynthesis [159].…”

A Chinese White Pear (Pyrus bretschneideri) BZR Gene PbBZR1 Act as a Transcriptional Repressor of Lignin Biosynthetic Genes in Fruits

“…A dual luciferase reporter assay was used in plant cells. These data presented that co-expression of these three pBD-PbBZR proteins are able to significantly inhibit the expression of the LUC reporter by co-expression with the individual reporter plasmid, indicating that these BZR transcription factors were possibly transcriptional repressors and had no transactivation activity ( Figure 5B ), which was similar to MaBZR1 and MaBZR2 ( Guo et al, 2018 ).…”

Transient Gene Expression is an Effective Experimental Tool for the Research into the Fine Mechanisms of Plant Gene Function: Advantages, Limitations, and Solutions

“…Note that the selection of a particular fluorescent protein for localizing the target gene product is dictated by the predicted localization in the plant cell. In particular, green fluorescent protein has proved to be an effective reporter in many experiments on verification of target protein localization in the nucleus [ 44 , 45 ], cytoplasm [ 31 , 46 ], plasma membrane [ 46 ], Golgi apparatus [ 41 ], endoplasmic reticulum (ER) [ 31 , 41 ], tonoplast [ 47 ], mitochondria [ 48 ], and chloroplasts [ 41 ], while, in addition to green fluorescent protein, yellow fluorescent protein (YFP) and mCherry could be used to assess localization in peroxisomes, as recently demonstrated [ 38 , 43 ].…”