Cytochrome c and the transcription factor ABI4 establish a molecular link between mitochondria and ABA-dependent seed germination.

During germination, seed reserves are mobilised to sustain the metabolic and energetic demands of plant growth. Mitochondrial respiration is presumably required to drive germination in several species, but only recently its role in this process has begun to be elucidated. Using Arabidopsis thaliana lines with changes in the levels of the respiratory chain component cytochrome c (CYTc), we investigated the role of this protein in germination and its relationship with hormonal pathways.

Class I TCP proteins TCP14 and TCP15 are required for elongation and gene expression responses to auxin.

Two class I TCP transcription factors are required for an efficient elongation of hypocotyls in response to auxin and for the correct expression of a subset of auxin-inducible genes In this work, we analyzed the response to auxin of plants with altered function of the class I TEOSINTE BRANCHED 1, CYCLOIDEA, PCF (TCP) transcription factors TCP14 and TCP15. Several SMALL AUXIN UP RNA (SAUR) genes showed decreased expression in mutant plants defective in these TCPs after an increase in ambient temperature to 29 °C, a condition that causes an increase in endogenous auxin levels. Overexpression of SAUR63 caused a more pronounced elongation response in the mutant than in the wild-type at 29 °C, suggesting that the decreased expression of SAUR genes is partly responsible for the defective elongation at warm temperature.

Class-I TCP Transcription Factors Activate the Gene Subfamily in Gibberellin-Dependent Stamen Filament Elongation.

In autogamous plants like Arabidopsis (), stamen filament elongation must be finely regulated to ensure that anthers reach the pistil at the correct developmental stage. In this work, we studied the roles of Arabidopsis TEOSINTE BRANCHED1, CYCLOIDEA, PCF15 (TCP15), and related class-I TCP transcription factors in stamen filament elongation. Plants with decreased expression of class-I TCPs and plants that express a fusion of TCP15 to a repressor domain (::-) had shorter stamens, indicating that class-I TCPs stimulate filament growth.