MADS-Box and bHLH Transcription Factors Coordinate Transmitting Tract Development in Arabidopsis thaliana

Abstract

The MADS-domain transcription factor SEEDSTICK (STK) controls several aspects of plant reproduction. STK is co-expressed with CESTA (CES), a basic Helix-Loop-Helix (bHLH) transcription factor-encoding gene. CES was reported to control redundantly with the brassinosteroid positive signaling factors BRASSINOSTEROID ENHANCED EXPRESSION1 (BEE1) and BEE3 the development of the transmitting tract. Combining the stk ces-4 mutants led to a reduction in ovule fertilization due to a defect in carpel fusion which, caused the formation of holes at the center of the septum where the transmitting tract differentiates. Combining the stk mutant with the bee1 bee3 ces-4 triple mutant showed an increased number of unfertilized ovules and septum defects. The transcriptome profile of this quadruple mutant revealed a small subset of differentially expressed genes which are mainly involved in cell death, extracellular matrix and cell wall development. Our data evidence a regulatory gene network controlling transmitting tract development regulated directly or indirectly by a STK-CES containing complex and reveal new insights in the regulation of transmitting tract development by bHLH and MADS-domain transcription factors.

The Arabidopsis MADS-Domain Transcription Factor SEEDSTICK Controls Seed Size via Direct Activation of E2Fa

“…In particular, MADS-domain transcription factors have been found to be key determinants of female reproductive development [13]. Among them, the Arabidopsis transcription factor SEEDSTICK (STK) has been largely studied in relation to its function in ovule identity determination [14,15], transmitting tract development [16,17] seed abscission [15,18], seed coat development [19] and flavonoid biosynthesis [20]. We have also previously shown how STK regulates size and differentiation of fruits by providing a link between signaling hormones (cytokinins) and other molecular developmental networks [21].…”

Paving the Way for Fertilization: The Role of the Transmitting Tract

“…HEC gene products modulate postgenital fusion of the septum and consequently TT development; HEC genes interact with SPT and together specify TT formation and development. As well as HEC transcription factors, HAF, BEE1, and BEE3 redundantly specify TT formation, being involved in ECM production, and besides this, they modulate cell death in the TT [ 34 , 35 ]. Recently, the MADS-box transcription factor SEEDSTICK was shown to act with NTT in the TT cell degradation process [ 36 ].…”

“…With this brief depiction of TT formation and development, we only show a small portion of the knowledge about this process, which is much more complex and finely regulated, involving the interaction of these regulatory gene networks with hormone signaling, such as auxin, cytokinin, and brassinosteroids. This has been extensively reviewed in [ 22 , 34 , 35 ]. The more recent work demonstrated the AHK cytokinin receptors expressed in the gynoecium to have redundant and specialized functions in this tissue of Arabidopsis [ 38 ].…”

Building a Flower: The Influence of Cell Wall Composition on Flower Development and Reproduction

“…In this region, two TFs, SEEDSTICK (STK) and NO TRANSMITTING TRACT (NTT) were identified as regulating cell wall degradation processes [ 89 ]. Other key players regulating transmitting tract formation include several bHLH TFs (SPATULA, HECATE, and HALF FILLED) [ 90 , 91 ]. Additionally, the master regulators control specific aspects of developmental processes related to the cell wall, such as STK in the control of the seed coat [ 92 , 93 ] and lignification in the funiculus for seed abscission [ 94 ].…”