Overexpression of AtbHLH112 suppresses lateral root emergence in Arabidopsis.

The basic/helix-loop-helix (bHLH) transcription factors are ubiquitous transcriptional regulators that control many different developmental and physiological processes in the eukaryotic kingdom. In this study, the function of AtbHLH112, an uncharacterised member of the bHLH family in Arabidopsis was investigated. Overexpression of AtbHLH112 suppressed lateral root (LR) development in Arabidopsis seedlings. Examination under the microscope revealed that abnormal lateral root primordia (LRP) with flat-head and more than four cell layers retained in the endodermal layer account for over 45% of the total number of LRP and LRs. This suggests that LRP emergence was prevented before LRP penetrated the cortical layer in the transgenic lines. Decreased auxin level within the LRP and parental root cells surrounding the LRP, as well as downregulated expression of cell-wall-remodelling (CWR) genes in the roots may contribute to the suppression of LR emergence in AtbHLH112-overexpressing lines. This finding was further supported by the observation that exogenous application of auxin recovered LR development and upregulated the expression of CWR genes in AtbHLH112-overexpressing lines. Lateral root emergence is tightly regulated, although molecular components involved in this process are still largely unknown. This study showed that overexpression of a basic/helix-loop-helix (bHLH) transcription factor AtbHLH112 specifically suppresses lateral root emergence by decreasing the local auxin level and downregulating expression of cell-wall-remodelling (CWR) genes. Our results suggest that AtbHLH112 may represent a novel repressor of cell separation during lateral root emergence. [ABSTRACT FROM AUTHOR]