Table 1.
List of the key players that are involved in TT formation and development in Arabidopsis thaliana.
| Proteins | Type | Function | Expression Pattern | Phenotype of loss-of-function mutants | References |
|---|---|---|---|---|---|
| NO TRANSMITING TRACT (NTT) | C2H2/C2HC zinc finger transcription factor | Transmitting tract (TT) development; extracellular matrix (ECM) production and TT programed cell death (PCD) | TT | Non functional TT defective ECM production and defective PCD |
[25] |
| ETTIN (ETT) | Auxin response transcription factor | Correct gynoecium formation | Gynoecium; valves; developing ovules | Everted TT develops in valve tissues & on regions with missing valves | [26] |
| SPATULA (SPT) | bHLH (basic helix-loop-helix) transcription factor | Acts redundantly with ALC to control development of carpel margin tissues | Developing carpel margin tissues | Unfused carpels; TT is absent; exhibits defects in post-genital fusion of the septum | [21,28] |
| SEUSS (SEU) | Transcriptional co-regulator | Development of the carpel margin meristem (meristematic structure located on the margins of the fused carpels and gives rise to ovules, septum, and TT) | Carpel margin meristem and ovules | Partial splitting of the gynoecial apex; seu ant double mutants exhibit ovule defects & 50% of the gynoecia do not develop a TT | [29] |
| AINTEGUMENTA (ANT) | Putative transcriptional regulator | Ovule development; TT development | Floral organs primordia & developing ovules. | Fail to produce ovules with integuments & functional female gametophyte; seu ant double mutants exhibit ovule defects & 50% of the gynoecia do not develop a TT | [29] |
| ALCATRAZ (ALC) | myc/bHLH transcription factor-like protein | Acts redundantly with SPT to control development of carpel margin tissues; fruit dehiscence | Developing carpel margin tissues; TT; stigma | Disruption of septum & gynoecium fusion; defects in TT development. Fruit dehiscence impaired | [30] |
| INDEHISCENT (IND) | bHLH DNA-binding superfamily protein | Valve margin development and silique dehiscence. TT development | Valve margins | Disruption of septum and gynoecium fusion. Fruits fail to open on maturity. | [31] |
| HECATE 1, 2 and 3 (HEC1, HEC2, HEC3) | bHLH transcription factors | Modulate post-genital fusion of the septum, and consequently TT development | Developing septum, TT and ovules | Infertility, defects in septum, TT and stigma development and impaired pollen tube growth | [33] |
| HALF FILLED (HAF) / CESTA (CES) | Transcription factor | Acts redundantly with BEE1 & BEE3 to specify reproductive tract tissues | Septum, TT and funiculus | In haf bee1 bee3 ECM formation and PCD fail to occur within the TT; reduced pollen tube growth | [34] |
| BRASSINOSTEROID ENHANCED EXPRESSION1 and 3 (BEE1, BEE3) | bHLH transcription factor | Acts redundantly with HAF to specify reproductive tract tissues | BEE1: stigma & top of the style.BEE3 TT and style.: | In haf bee1 bee3 ECM formation and PCD fail to occur within the TT; reduced pollen tube growth | [34] |
| SEEDSTICK (STK) | MADS-box transcription factor | Ovule identity; normal seed shedding; seed coat development; TT PCD | Septum and ovules | Fail to release seeds; Separation of abscission zone cells fails; fruits are shorter; abnormal positioning of seeds | [36,37] |