Gene Networks and Chromatin and Transcriptional Regulation of the Phaseolin Promoter in Arabidopsis

Abstract

The complete lack of seed storage protein expression in vegetative tissues and robust expression during embryogenesis makes seed development an ideal system to study tissue-specific expression of genes. The promoter for the Phaseolin (phas) gene, which encodes the major seed storage protein in bean (Phaseolus vulgaris), is activated in two sequential steps: Phaseolus vulgaris ABI3-like factor (Pv-ALF)-dependent potentiation and abscisic acid-mediated activation. In this study, a heterologous in vivo Pv-ALF/phas-GUS (for b-glucuronidase) expression system in transgenic Arabidopsis thaliana leaves was used in conjunction with the powerful RNA-Seq approach to capture transcriptional landscapes of phas promoter expression. Remarkably, expression of over 1300 genes from 11 functional categories coincided with changes in the transcriptional status of the phas promoter. Gene network analysis of induced genes and artificial microRNA-mediated loss-of-function genetic assays identified transcriptional regulators RINGLET 2 (RLT2) and AINTEGUMENTA-LIKE 5 (AIL5) as being essential for phas transcription. Pv-ALF binding to the RLT2 and AIL5 promoter regions was confirmed by electrophoretic mobility shift assay. RLT2 and AIL5 knockdown lines displayed reduced expression of several endogenous seed genes, suggesting that these factors are involved in activation of endogenous Arabidopsis seed storage gene expression. Overall, the identification of these key factors involved in phas activation provides important insight into the two-step transcriptional regulation of seed-specific gene expression.

The BABY BOOM Transcription Factor Activates the LEC1-ABI3-FUS3-LEC2 Network to Induce Somatic Embryogenesis

“…Our data now place BBM/AIL proteins directly upstream of the LAFL/AGL15 genes. There is some evidence that LAFL proteins might act upstream of AILs: a Phaseolus vulgaris ABI3-like factor (PvALF) binds and activates Arabidopsis CHO1/EMK/AIL5/ PLT5 (Sundaram et al, 2013), and Arabidopsis FUS was shown to bind BBM, PLT2, AIL6/PLT3, and PLT7, although transcriptional regulation was not investigated (Wang and Perry, 2013). In contrast, the lack of AIL deregulation after inducible overexpression of LEC1, ABI3, FUS3, or LEC2 (Braybrook and Harada, 2008;Yamamoto et al, 2010;Junker et al, 2012;Mönke et al, 2012) suggests that there is no direct feedback of LAFLs on AILs.…”

Transcription Factors in the Regulation of Somatic Embryogenesis

“…Although our knowledge about the PLT-mediated induction of SE is rather fragmentary, a recent finding that PLT3, EMK/PLT5 and PLT7 stimulate auxin biosynthesis through the activation of YUC genes (YUC1 and YUC4) to control phyllotaxis (Pinon et al 2013) implies a possible role of PLTs in the auxin-related mechanism of SE induction. An EMK/PLT5-controlled induction of SE may also be related to GA and an encoded TF was reported to negatively impact GA biosynthesis in the control of the storage protein accumulation in Arabidopsis seeds (Sundaram et al 2013).…”

Seed-Specific Expression of a Feedback-Insensitive Form of CYSTATHIONINE-γ-SYNTHASE in Arabidopsis Stimulates Metabolic and Transcriptomic Responses Associated with Desiccation Stress

“…S1). This promoter is the most abundant seed storage protein in the common bean (Phaseolus vulgaris) and is stringently turned off during all vegetative stages of plant development (Sundaram et al, 2013). It was also demonstrated that this promoter is induced constitutively during the maturation and desiccation stages of seed development (Fait et al, 2011).…”

“…This fragment was cut from the pCE vector using SphI and introduced with that enzyme into the pCEPH vector, which contains the phaseolin promoter (Shaul and Galili, 1992). This promoter is the most abundant seed storage protein in the common bean (Phaseolus vulgaris) and is stringently turned off during all vegetative stages of plant development (Sundaram et al, 2013). It was demonstrated that this promoter is induced constitutively during the maturation and desiccation stages of seed development (Fait et al, 2011).…”