Identification and Characterization of the Sucrose Synthase 2 Gene (Sus2) in Durum Wheat.

Mariateresa Volpicella,Bruno Gattulli,Agata Gadaleta,Immacolata Fanizza,Antonio Blanco,Luigi R Ceci,Claudia Leoni,Giacomo Mangini,Domenica Nigro

doi:10.3389/fpls.2016.00266

Abstract

Sucrose transport is the central system for the allocation of carbon resources in vascular plants. Sucrose synthase (SUS), which reversibly catalyzes sucrose synthesis and cleavage, represents a key enzyme in the control of the flow of carbon into starch biosynthesis. In the present study the genomic identification and characterization of the Sus2-2A and Sus2-2B genes coding for SUS in durum wheat (cultivars Ciccio and Svevo) is reported. The genes were analyzed for their expression in different tissues and at different seed maturation stages, in four tetraploid wheat genotypes (Svevo, Ciccio, Primadur, and 5-BIL42). The activity of the encoded proteins was evaluated by specific activity assays on endosperm extracts and their structure established by modeling approaches. The combined results of sucrose synthase 2 expression and activity levels were then considered in the light of their possible involvement in starch yield.

Highlights

Starch is the major reserve carbohydrate in plants and its production is critical to both yield and overall quality of grain
To physically map the two Sus2 genes and validate the putative genome assignment of the two DNA sequences obtained, a set of nulli-tetrasomic lines (NTs) for all chromosome groups was amplified with the same genomic-specific primer pairs (Supplementary Table S1 and Figure S2), leading to the same PCR products
The present report describes the identification of the wheat Sus2 gene sequences in durum wheat cvs Ciccio and Svevo, together with their expression analysis carried out by RTPCR and activity assays of encoded enzymes, compared to other two different genotypes (Primadur, 5-BIL42), chosen for their differences in important qualitative and quantitative traits, including grain yield components (Blanco et al, 2012; Pasqualone et al, 2015)

Summary

Introduction

Starch is the major reserve carbohydrate in plants and its production is critical to both yield and overall quality of grain. It constitutes approximately 70% of mature grain dry weight and its characteristics directly affect on the nature and quality of flour and related products (Kim et al, 2003). The first one is the structural gene for the major endosperm isoform of the enzyme that is anaerobically induced in roots and shoots, while the second is the structural gene for the constitutively expressed isoenzyme in embryo and other tissues. Sus gene is predominantly expressed in the endosperm, while Sus gene is expressed in roots and leaves, where it is induced under

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