Diversity and Functional Dynamics of Fleshy Fruit Abscission Zones

Abstract

We examine the current knowledge about the abscission of fleshy fruit, in particular with regards to the development and function of the abscission zone (AZ). While tomato is currently the main model species to elucidate the mechanisms of fleshy fruit abscission, most studies on tomato focus on the development and function of the pedicel AZ, which is involved in both flower and ripe fruit abscission. However, the localization of the AZ within the pedicel is not the most common location of the AZ for fleshy fruit. Fleshy fruit can have one or more AZ, which can be found in different locations within the inflorescence and fruiting structure and fulfil different functions. In fact, most of the fleshy fruit species examined thus far have more than one AZ, which can be found at the boundary between the fruit and pedicel (often referred to as the calyx AZ), within the pedicel as with tomato, at the juncture of the pedicel and peduncle or at the juncture between peduncle and shoot/branch. In addition, the different AZs may be activated or function at different stages of development, under different environmental conditions, or have a completely different purpose, such as the abscission of fruitlets or mature fruit. Together, our current knowledge about AZs suggests that while there are similarities between different AZs in different locations or from different species, not all AZs are created equal, which may be reflected in the underlying molecular mechanisms that control their development and function.

Multi-scale comparative transcriptome analysis reveals key genes and metabolic reprogramming processes associated with oil palm fruit abscission

“…Indeed, fleshy fruit abscission is an important agronomic trait with widespread economic consequences [2]. Fruit bearing species with overly abundant immature fruit need to be thinned to obtain the optimal size and highest quality fruit.…”

“…The jointless tomato, which lacks a functional AZ, exemplifies the central role of the AZ for the abscission process [1]. Abscission zones can be classified into two general types based on their anatomy: 1) at the boundary region at the base of the organ to be shed and the neighbouring tissue, for example between a floral organ and the pedicel as observed in Arabidopsis or between the mesocarp and the pedicel as observed in oil palm fruit, and 2) within a tissue as observed in the pedicel of the tomato fruit or flower [2,4]. While the differentiation of these two AZ types may be different, in both cases once the AZ develops at the base of the organ to be shed, they must acquire competence to respond to signals required for cell separation and organ abscission [4,6,[11][12][13][14].…”

A tomato prolyl-4-hydroxylase causes relocation of abscission zone and alters abscission kinetics

“…Abscission is the process of organ separation, a highly coordinated biological programme regulated predominantly by ethylene and auxin, while hormones such as giberrelins, cytokinins, abscisic acid and jasmonic acid also participate in the timing of abscission initiation (Tucker and Kim, 2015;Tranbarger and Tadeo, 2020;Sundaresan et al, 2016). The primary abscission model for plant species are Arabidopsis, tomato and soybean for flower organ, flower and fruit pedicel and leaf abscission, respectively.…”

IDA (INFLORESCENCE DEFICIENT IN ABSCISSION)-like peptides and HAE (HAESA)-like receptors regulate corolla abscission in Nicotiana benthamiana flowers

“…Abscission is a fundamental cell separation process in plant biology that accounts for a highly beneficial evolutionary adaptation for plants: the discarding of infected, senescent or physiologically damaged organs and the highly efficient seed dispersal [1]. However, from an agricultural point of view, abscission has a huge impact on yield, leading to high production losses.…”