Abstract
Auxin response factors (ARFs) encode transcriptional factors that function in the regulation of plant development processes. A tomato ARF gene, SlARF5, was observed to be expressed at high levels in emasculated ovaries but maintained low expression levels in pollinated ovaries. The amiRNA SlARF5 lines exhibited ovary growth and formed seedless fruits following emasculation. These parthenocarpic fruits developed fewer locular tissues, and the fruit size and weight were decreased in transgenic lines compared to those of wild-type fruits. Gene expression analysis demonstrated that several genes involved in the auxin-signaling pathway were downregulated, whereas some genes involved in the gibberellin-signaling pathway were enhanced by the decreased SlARF5 mRNA levels in transgenic plants, indicating that SlARF5 may play an important role in regulating both the auxin- and gibberellin-signaling pathways during fruit set and development.
Highlights
The plant hormone auxin, indole-3-acetic acid (IAA), plays an important role in various aspects of plant development, such as cell extension, division, and differentiation, as well as in organ and tissue development, and tropism
SlARF7 functions as a negative regulator of fruit set until pollination and fertilization have occurred[18]
Auxin response factors (ARFs) encode important transcription factors and regulate gene expression in response to auxin by binding to the TGTCTC sequence in the auxin response elements found in the promoters of primary/ early auxin response genes
Summary
The plant hormone auxin, indole-3-acetic acid (IAA), plays an important role in various aspects of plant development, such as cell extension, division, and differentiation, as well as in organ and tissue development, and tropism. Functional studies have demonstrated that ARF genes play an essential role in signal transduction during plant organ development. Biochemical analyses have identified two peaks in auxin levels during tomato fruit development: the first at 8 d after pollination at the end of active cell division, and the other at 30 d after pollination[22], corresponding to cell expansion (stage III) and the fruit maturation stage (stage IV), thereby suggesting that auxin has an important role in promoting fruit cell expansion[22,23,24] and initiating and enhancing climacteric ripening[25]. Previous studies have demonstrated that the expansion of tomato locular cells coinciding with the expression of genes encoding for water flow, organic acid synthesis, sugar storage, and photosynthesis is regulated by auxin and GA30. Certain other genes, including TAGL1 (SHATTERPROOF)[35], MYB factors[36], and SlPPC2 (phosphoenolpyruvate carboxylase)[37], may regulate fruit cell expansion in tomato
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