GhFAD2\u20133 is required for anther development in Gossypium hirsutum

Feng Liu,Xinyu Zhang,Lihong Ma,Yanjun Li,Xinhui Nie,Youwu Wang,Qianhao Zhu,Fei Xue,Jie Sun

doi:10.1186/s12870-019-2010-9

Abstract

BackgroundIn higher plants, the FAD2 gene encodes the microsomal oleate Δ12-desaturase, one of the key enzymes essential for the biosynthesis of the polyunsaturated lipids that serve many important functions in plant development and stress responses. FAD2 catalyzes the first step, in the biosynthesis of the polyunsaturated fatty acids (PUFAs) found in the cell membrane and cell wall, and it is thus of great importance to investigate the regulatory role of FAD2 in anther development.ResultsWe reported the molecular characterization of the cotton (Gossypium hirsutum) GhFAD2 gene family and the essential role of GhFAD2–3 in cotton anther development. G. hirsutum contains four pairs of homoeologous FAD2 genes (GhFAD2–1 to GhFAD2–4). GhFAD2–3 is ubiquitously and relatively highly expressed in all analyzed tissues, particularly in anthers. Specific inhibition of GhFAD2–3 using the RNA interference approach resulted in male sterility due to impaired anther development at the stages from meiosis to maturation. The cellular phenotypic abnormality observed at the meiosis stage of the GhFAD2–3 silenced plant (fad2–3) coincides with the significant reduction of C18:2 in anthers at the same stage. Compared with that of the wild type (WT), the content of C18:1 was 41.48%, which increased by 5 fold in the fad2–3 anther at the pollen maturation stage. Moreover, the ratio of monounsaturated to polyunsaturated fatty acid was 5.43 in fad2–3 anther, which was much higher than that of the WT (only 0.39). Through compositional analysis of anthers cuticle and transcriptome data, we demonstrated it was unfavorable to the development of anther by regulating GhFAD2–3 expression level to increase the oleic acid content.ConclusionsOur work demonstrated the importance of C18:2 and/or C18:3 in the development of the pollen exine and anther cuticle in cotton and provided clue for further investigation of the physiological significance of the fatty acid composition for plant growth and development.

Highlights

In higher plants, the FAD2 gene encodes the microsomal oleate Δ12-desaturase, one of the key enzymes essential for the biosynthesis of the polyunsaturated lipids that serve many important functions in plant development and stress responses
We demonstrated that silencing of GhFAD2–3 resulted in male sterility, due to nonviable pollen grains and abnormal anther development resulted from significantly reduced levels of polyunsaturated fatty acids (PUFAs) at the meiosis and tetrad stages
Five and nine putative FAD2 genes were identified in G. arboreum (Ga), G. raimondii (Gr) and G. hirsutum (Gh), respectively

Summary

Introduction

The FAD2 gene encodes the microsomal oleate Δ12-desaturase, one of the key enzymes essential for the biosynthesis of the polyunsaturated lipids that serve many important functions in plant development and stress responses. FAD2 catalyzes the first step, in the biosynthesis of the polyunsaturated fatty acids (PUFAs) found in the cell membrane and cell wall, and it is of great importance to investigate the regulatory role of FAD2 in anther development. The microsomal oleate Δ12-desaturase (fatty acid desaturase 2, FAD2) is a hydrophobic endoplasmic reticulum protein, catalyzing the reaction from monounsaturated oleic acid (C18:1) to polyunsaturated linoleic acid (C18:2) by introducing a double bond between the 12th and 13th carbon atoms of C18:1 [1]. As the key gene controlling the conversion of C18:1 to C18:2, the FAD2 transcriptional level directly determines the relative content and proportion of polyunsaturated fatty acids (PUFAs) in plants [9]. Due to the oxidative instability of PUFAs, studies on the regulation of FAD2 were mainly focused on reducing its expression level to decrease the C18:2 content in oil seeds, and to improve oil quality [4, 12,13,14,15,16]

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