PbGA20ox2 Regulates Fruit Set and Induces Parthenocarpy by Enhancing GA4 Content

Abstract

Fruit set and development occur following successful fertilization. Parthenocarpy, a valuable trait in some self-incompatible species, produces seedless fruit without fertilization. Gibberellin (GA) is a crucial hormone in fruit-set regulation and development. While investigating the development of parthenocarpy in pear (Pyrus bretschneideri Rehd.), we determined that GA 20-oxidases (GA20ox) may play key roles in seedless pear fruit development. Sequence analysis revealed three PbGA20ox genes: PbGA20ox1, PbGA20ox2, and PbGA20ox3. We analyzed the expression patterns of candidate genes and found that PbGA20ox2 levels significantly changed in pollinated fruits. Tissue-specific expression assays revealed that PbGA20ox2 is highly expressed in young fruit and leaves. Subcellular localization assays showed it was located in the cytoplasm, nucleus, and plasma membrane. Overexpressed PbGA20ox2 tomato plants were taller and had longer hypocotyls and internodes, and the emasculated flowers produced parthenocarpic fruit. In pear, the transient overexpression of PbGA20ox2 promoted fruit development and delayed the drop of nonpollinated fruit. Furthermore, the fruit of PbGA20ox2-overexpressing tomato and transient PbGA20ox2overexpressing pear had increased GA 4 (but not GA 3 and GA 1 ) contents. This result provided evidence that PbGA20ox2 was necessary for GA 4 -dependent pear fruit development. Our study revealed that PbGA20ox2 altered the GA biosynthetic pathway and enhanced GA 4 synthesis, thereby promoting fruit set and parthenocarpic fruit development.

SlTPL1 Silencing Induces Facultative Parthenocarpy in Tomato

“…Thus, exogenous IAA or GA treatment can trigger parthenocarpy without the need for pollination or fertilization ( Mazzucato et al, 1999 ; de Jong et al, 2009a ). Consistently, high IAA and GA levels are found in some parthenocarpic fruit mutants ( Fos et al, 2000 ; Takisawa et al, 2018 ; Wang et al, 2020 ). The same situation was found in facultative parthenocarpic fruit; increased IAA and GA levels have been found in some facultative parthenocarpic mutants, such as pat , pat2 , and Auccisa ( Mazzucato et al, 1998 ; Fos et al, 2000 ; Molesini et al, 2009 ; Ribelles et al, 2019 ).…”

“…Thus, exogenous IAA or GA treatment can trigger parthenocarpy without the need for pollination or fertilization (Mazzucato et al, 1999;de Jong et al, 2009a). Consistently, high IAA and GA levels are found in some parthenocarpic fruit mutants (Fos et al, 2000;Takisawa et al, 2018;Wang et al, 2020).…”

“…Parthenocarpic fruit-set can be attained by natural genetic manipulation ( Ficcadenti et al, 1999 ; Carmi et al, 2003 ), induction via exogenous application of phytohormones (auxins, CKs, and GAs) to the ovary ( de Jong et al, 2009a ; Ding et al, 2013 ), elevating the levels of these endogenous phytohormones, or enhancing the response of ovaries and ovules to auxins and GAs ( de Jong et al, 2009a ; Wang et al, 2009 ; Takisawa et al, 2018 ; Matsuo et al, 2020 ; Wang et al, 2020 ). At the molecular level, GA is the key hormone in the fruit-set process.…”

Downstream of GA4, PbCYP78A6 Regulates Parthenogenesis by Mediating Cell Cycle-Related Genes in Pear (Pyrus Bretshneider Rehd.)

“…Exogenous applications of multiple hormones mimic fertilization functions and fruit set, independently of fertilization, resulting in parthenocarpy [9,23]. In 'Dangshansu' pear, GA 4 is effective in inducing parthenocarpy [10][11][12]24], whereas GA 3 does not induce parthenocarpy. Here, the difference between GA 4 -and GA 3 -induction in pear was assessed to investigate the mechanisms of parthenocarpy-related downstream hormones.…”

Jasmonic Acid and Ethylene Participate in the Gibberellin-Induced Ovule Programmed Cell Death Process in Seedless Pear ‘1913’ (Pyrus hybrid)

“…The samples used in study were collected from a pear orchard in Meixian, Shaanxi, China, in 2021 (34.29° N, 107.76° E, 514 m above sea level) [ 45 ]. The average annual precipitation at this location was 574.6 mm, and the average annual temperature was 12.7 °C.…”