Molecular Characterization of Rice OsLCB2a1 Gene and Functional Analysis of its Role in Insect Resistance.

Mahfuj A Begum,Ye Tan,Cungui Mao,Xiao-Xiao Shi,Zeng-Rong Zhu,Wen-Wu Zhou,Lina Obeid,Yusuf Hannun

doi:10.3389/fpls.2016.01789

Abstract

In plants, sphingolipids, such as long-chain bases (LCBs), act as bioactive molecules in stress responses. Until now, it is still not clear if these lipids are involved in biotic stress responses to herbivore. Herein we report that a rice LCB gene, OsLCB2a1 encoding a subunit of serine palmitoyltransferase (SPT), a key enzyme responsible for the de novo biosynthesis of sphingolipids, plays a critical role in plant defense response to the brown planthopper (BPH) attack and that its up-regulation protects plants from herbivore infestation. Transcripts of OsLCB2a1 gene in rice seedlings were increased at 4 h, but decreased at 8–24 h after BPH attack. Sphingolipid measurement profiling revealed that overexpression of OsLCB2a1 in Arabidopsis thaliana increased trihydroxylated LCB phytosphingosine (t18:0) and phytoceramide by 1.7 and 1.3-fold, respectively, compared with that of wild type (WT) plants. Transgenic Arabidopsis plants also showed higher callose and wax deposition in leaves than that of WT. Overexpression of OsLCB2a1 gene in A. thaliana reduced the population size of green peach aphid (Myzus persicae). Moreover, the electrical penetration graph (EPG) results indicated that the aphids encounter resistance factors while reaching for the phloem on the transgenic plants. The defense response genes related to salicylic acid signaling pathway, remained uplgulated in the OsLCB2a1-overexpressing transgenic plants. Our data highlight the key functions of OsLCB2a1 in biotic stress response in plants.

Highlights

Sphingolipids, a group of lipids, are essential structural components of the endomembrane system present in a variety of organisms including eukaryotes and bacteria (Lynch and Dunn, 2004; Hannun and Obeid, 2008; Merrill et al, 2009)
To investigate the possible function of sphingolipid in insect resistance response, we cloned a gene (Os01g70380) from O. sativa encoding the LCB2a subunit of Serine palmitoyltransferase (SPT), designated as OsLCB2a1
The full-length cDNA of the OsLCB2a1 gene was amplified by RT-PCR

Summary

Introduction

Sphingolipids, a group of lipids, are essential structural components of the endomembrane system present in a variety of organisms including eukaryotes and bacteria (Lynch and Dunn, 2004; Hannun and Obeid, 2008; Merrill et al, 2009). They are a group of lipids containing a backbone of sphingoid bases (1, 3- dihydroxy- 2-amino- alkane and its derivatives), a set of aliphatic amino alcohols that includes sphingosine. SPT is anchored to the endoplasmic reticulum (Hanada, 2003) Both LCB1 and LCB2 sub-units are conserved in plants and are required for the function of SPT (Chen et al, 2006; Dietrich et al, 2008). Sphinganine can be further modified by the addition of a hydroxyl group at C4 to yield phytosphingosine and/or by introduction of double bonds at C4 and C8 to produce other LCBs (Lynch and Dunn, 2004)

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