4-CPA (4-Chlorophenoxyacetic Acid) Induces the Formation and Development of Defective “Fenghou” (Vitis vinifera × V. labrusca) Grape Seeds

Abstract

For some horticultural plants, auxins can not only induce normal fruit setting but also form fake seeds in the induced fruits. This phenomenon is relatively rare, and, so far, the underlying mechanism remains unclear. In this study, “Fenghou” (Vitis vinifera × V. labrusca) grapes were artificially emasculated before flowering and then sprayed with 4-CPA (4-chlorophenoxyacetic acid) to analyze its effect on seed formation. The results show that 4-CPA can induce normal fruit setting in “Fenghou” grapes. Although more seeds were detected in the fruits of the 4-CPA-treated grapevine, most seeds were immature. There was no significant difference in the seed shape; namely, both fruit seeds of the grapevines with and without 4-CPA treatment contained a hard seed coat. However, the immature seeds lacked embryo and endosperm tissue and could not germinate successfully; these were considered defective seeds. Tissue structure observation of defective seeds revealed that a lot of tissue redifferentiation occurred at the top of the ovule, which increased the number of cell layers of the outer integument; some even differentiated into new ovule primordia. The qRT-PCR results demonstrated that 4-CPA application regulated the expression of the genes VvARF2 and VvAP2, which are associated with integument development in “Fenghou” grape ovules. Together, this study evokes the regulatory role of 4-CPA in the division and continuous redifferentiation of integument cells, which eventually develop into defective seeds with thick seed coats in grapes.

MADS-Box Protein Complex VvAG2, VvSEP3 and VvAGL11 Regulates the Formation of Ovules in Vitis vinifera L. cv. ‘Xiangfei’

“…The cDNA synthesis was initiated from 2 µg total RNA using a reverse transcription kit (Promega, Madison, WI, USA), and the procedure was as follows: the samples were incubated for 5 min at 70 °C and 1 h at 42 °C, and then placed on ice immediately. The qRT–PCR analyses were conducted on an ABI PRISM 7500 system (Thermo Fisher Scientific, Waltham, MA, USA) as described previously in Liu et al [ 25 ]. The reaction volume of qRT–PCR was 10 μL 2× Bestar SybrGreen qPCR Mastermix (DBI, Ludwigshafen, Germany) + 6 μL double distilled water (ddH2O) + 2 μL sample cDNA (0.025 μg) + 0.8 μL forward primers + 0.8 μL reverse primer + 0.4 μL 50× ROX Reference Dye.…”