Abstract Detail

Reproductive biology

Jayasinghege, Charitha [1], Reinecke, Dennis M. [2], Waduthanthri, Kosala Dinuka [2], Ozga, Jocelyn A. [1].

Differential regulation of 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase genes by the auxins IAA and 4-Cl-IAA during pea fruit development.

In pea, young fruits senescence and will abscise if they do not contain developing seeds. 4-chloroindole-3-acetic acid (4-Cl-IAA), a naturally occurring auxin in pea, but not the other natural auxin IAA, can mimic the role of seeds in stimulating fruit (pericarp) development. Previous studies showed that the effect of these auxins on fruit development is likely due to their differential effect on the GA biosynthesis pathway, but differential regulation of ethylene pathways may also play an important role. ACC synthase (ACS) is considered as the rate limiting enzyme of ethylene biosynthesis. However, there is evidence that ACC oxidase (ACO) plays a prominent regulatory role in certain physiological processes. To further understand the role of ethylene in the auxin response of pea fruit, we monitored the transcript abundance of ethylene biosynthesis pathway genes (PsACS2, PsACS4, PsACO1, PsACO2, and PsACO3) in 2 days after anthesis (DAA) deseeded pericarps treated with IAA, 4-Cl-IAA, or ethephon (ethylene releasing agent). In response to seed removal, PsACS4 transcript abundance increased, with a coordinate increase in PsACO2 and PsACO3 transcript abundance in 2 DAA pericarps of pollinated fruits. Ethephon applied to deseeded pericarps increased transcript abundance of all PsACO genes, but not the PsACS genes. These data suggest that ethylene feed-forward regulates expression of PsACO genes leading to greater ethylene levels and thereby advancing pericarp senescence. Application of the pericarp growth promoting auxin 4-Cl-IAA to deseeded pericarps reduced PsACS4, PsACO2 and PsACO3 transcript abundance, but dramatically increased PsACO1 transcript levels. In contrast, IAA (which does not stimulate deseeded pericarp growth) had little or no effect on the transcript abundance of the PsACS or PsACO genes in deseeded pericarps. Although, gene expression of these pericarp PsACS and PsACO genes were differentially regulated by 4-Cl-IAA and IAA, both auxins induced similar pericarp ethylene evolution profiles. However, simultaneous application of 4-Cl-IAA or IAA with ethephon to deseeded pericarps indicates 4-Cl-IAA decreases ethylene response. It has recently been proposed that in addition to its role in ethylene biosynthesis, ACO proteins may have protein modification and other regulatory properties which in turn regulate ethylene signal transduction. Our data suggest that the ACO protein coded from PsACO1 may be a possible candidate for regulation of the ethylene signaling pathway for reduced ethylene sensitivity in pea fruit. Overall, these data suggest that regulation of ACO expression plays a prominent role in hormone regulation of early pericarp growth.

1 - University of Alberta, Agricultural, Food and Nutritional Science, 410 Agriculture/Forestry Centre , Edmonton, AB, T6G 2P5, Canada
2 - University of Alberta, 410 Agriculture/Forestry Centre, Edmonton, AB, T6G 2P5, Canada

Keywords:
auxin
Ethylene
fruit development
4-chloroindole-3-acetic acid .

Presentation Type: Poster:Posters for Topics
Session: P
Location: Hall D/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 5:30 PM
Number: PRP009
Abstract ID:1202
Candidate for Awards:CSPB President's Award for Best Student Presentation