Ethylene biosynthesis and perception in apple fruitlet abscission (Malus domestica L. Borck)

Abstract

Abscission was studied in immature apple fruits (cv. Golden Delicious) during the physiological drop. Fruitlet populations, characterized by different abscission potential, were analysed. Non-abscising fruitlets (NAF) were obtained from central flowers borne in clusters where all the lateral flowers had been removed at bloom while abscising fruitlets (AF) were derived from lateral fruitlets of trees sprayed with benzylaminopurine (BAP) at 200 ppm, 17 d after petal fall (APF), when the fruit cross diameter was about 10-12 mm. Fruit shedding, monitored at the end of the June drop, was significantly different in the two populations, being less than 10%, and more than 90%, in NAF and AF, respectively. In AF, fruit drop peaked around 33 d after petal fall (APF) and was preceded by an increase in ethylene around 20 d APF. Transcript analysis was performed from 17-24 d APF, since preliminary experiments pointed out that major changes in expression of abscission related genes occurred within this period. Transcript accumulation of genes involved in ethylene biosynthesis (MdACS5B and MdACO) and action (MdERS1, MdETR1, and MdCTR1) was studied in the seed, cortex, peduncle, and abscission zone (AZ) of the two fruit populations. MdACS5B and MdACO transcripts accumulated along the experimental period in AF population, even though at a different magnitude, while ethylene evolution declined after peaking at day three. MdETR1, MdERS1, and MdCTR1 expression patterns depended on tissue and/or population. The ERS/ETR ratio was higher in AF than in NAF populations. Overall results pointed out that apple fruitlet drop is preceded by a stimulation of ethylene biosynthesis and a gain in sensitivity to the hormone.

Evaluation of Reference Genes for the Relative Quantification of Apple stem grooving virus and Apple mosaic virus in Apple Trees

“…Finally, 5 lL of the PCR product were run in 1.5% agarose gel colored by Sybrgreen (Sigma-Aldrich) and visualized under UV light. Seven reference genes such as GAPDH [3], 18S rRNA [3], S19 [3], Ubiquitine [2], Rubisco [4], RNA polymerase [4] and b-actine [9] as well as for the two viruses ASGV and ApMV [12] were chosen. These internal genes are known as the most stable expression in apple tissues Table 1.…”

MADS Box Transcript Amount is Affected by Ethylene during Abscission

“…The studies performed on this species pointed out that auxin, ethylene and their interaction are of primary importance [12,13]. Briefly, it was previously found that a massive increase in MdACO1 transcript amount was concomitant with an increase in elements involved in the signal transduction pathway.…”

“…Briefly, it was previously found that a massive increase in MdACO1 transcript amount was concomitant with an increase in elements involved in the signal transduction pathway. Furthermore, the variation in transcript amount followed the increase in ethylene evolution [12]. In Arabidopsis, tomato, rice and several other species these genes are present as multigene families whose members may have specific functions depending on the tissue and/or developmental stage [14].…”

Characterization of Two Orthologs of REVERSION-TO-ETHYLENE SENSITIVITY1 in Apple

“…Studies of these ethylene receptors have focused on understanding their roles in apple shelf life by quantifying the levels of their mRNA and/or protein accumulation (Tatsuki & Endo, 2006;Tatsuki, Endo, & Ohkawa, 2007;Tatsuki, Hayama, & Nakamura, 2009;Wang et al, 2009;Wiersma et al, 2007). The transcript levels of MdETR1 and MdERS1 were also evaluated in a study of ethylene biosynthesis and perception in apple fruitlet abscission (Dal Cin, Danesin, Boschetti, Dorigoni, & Ramina, 2005).…”

“…To date, only MdCTR1 has been described in apple. The conserved 3' end of the MdCTR1 coding region (AY670703) was cloned by Dal Cin et al (2005). Its full length cDNA was characterized by several alternative splicing variants (DQ847147-DQ847149) (Wiersma et al, 2007).…”