Silencing of the Ortholog of DEFECTIVE IN ANTHER DEHISCENCE 1 Gene in the Woody Perennial Jatropha curcas Alters Flower and Fruit Development.

Chuan-Jia Xu,Mao-Sheng Chen,Zeng-Fu Xu,Mei-Li Zhao

doi:10.3390/ijms21238923

Abstract

DEFECTIVE IN ANTHER DEHISCENCE 1 (DAD1), a phospholipase A1, utilizes galactolipids (18:3) to generate α-linolenic acid (ALA) in the initial step of jasmonic acid (JA) biosynthesis in Arabidopsis thaliana. In this study, we isolated the JcDAD1 gene, an ortholog of Arabidopsis DAD1 in Jatropha curcas, and found that it is mainly expressed in the stems, roots, and male flowers of Jatropha. JcDAD1-RNAi transgenic plants with low endogenous jasmonate levels in inflorescences exhibited more and larger flowers, as well as a few abortive female flowers, although anther and pollen development were normal. In addition, fruit number was increased and the seed size, weight, and oil contents were reduced in the transgenic Jatropha plants. These results indicate that JcDAD1 regulates the development of flowers and fruits through the JA biosynthesis pathway, but does not alter androecium development in Jatropha. These findings strengthen our understanding of the roles of JA and DAD1 in the regulation of floral development in woody perennial plants.

Highlights

Jasmonic acid (JA) is one of several major phytohormones that plays a pivotal role in modulating plant growth and development, as well as in responding to various abiotic and biotic stresses [1,2,3,4]
The initial step of JA biosynthesis is the release of ALA from fatty acids in Arabidopsis chloroplasts, which is performed by two types of enzymes, fatty acid desaturases (FADs) and phospholipase A1 (PLA1) [7]
Similar to Arabidopsis and rice, JcDAD1 possesses only one exon accompanied by no introns (Figure 1A), indicating that DEFECTIVE IN ANTHER DEHISCENCE 1 (DAD1) is evolutionarily conserved among these plants

Summary

Introduction

Jasmonic acid (JA) is one of several major phytohormones that plays a pivotal role in modulating plant growth and development, as well as in responding to various abiotic and biotic stresses [1,2,3,4]. The initial step of JA biosynthesis is the release of ALA from fatty acids in Arabidopsis chloroplasts, which is performed by two types of enzymes, fatty acid desaturases (FADs) and phospholipase A1 (PLA1) [7]. Three sequential steps are catalyzed by 13-lipoxygenases (13-LOXs), allene oxide synthase (AOS), and allene oxide cyclase (AOC): oxygenation of ALA to 13-hydroperoxylinoleic acid (13-HPOT), dehydrogenation of 13-HPOT to the unstable compound 12,13-epoxyoctadecatrienoic acid (12,13-EOT), and cyclization of 12,13-EOT to (9S,13S)-12-oxo-phytodienoic acid (OPDA), respectively [8,9,10,11,12,13]. OPDA is synthesized in chloroplasts, transported to the peroxisomes by the transport protein peroxisomal ABC transporter 1 (PXA1) [14] and converted to 3-oxo-2-(2 (Z)-pentenyl)-cyclopentane-1-octanoic acid (OPC-8:0) by 12-oxo-phytodienoic acid reductase (OPR) [12]. JA is catalyzed via jasmonic acid carboxyl methyltransferase (JMT) to methyl jasmonate (MeJA) or by jasmonic acid-amino acid synthetase to jasmonic acid-amino acids, such as jasmonic acid-isoleucine (JA-Ile) [18]

Methods

Results

Conclusion