Genetic basis and molecular mechanism of wheat development

Abstract

Wheat is one of the most important crops in the world. Wheat can be classified according to its qualitative requirement for low temperature to accelerate flowering (i.e. vernalization). Winter wheat has a vernalization requirement whereas spring wheat does not. Winter wheat can be further classified according to its quantitative vernalization requirement: weak winter, semi-winter, and strong winter types. Three genes were cloned based on qualitative variation in vernalization requirement between spring and winter wheat, but genes controlling quantitative variation among winter wheat cultivars are not well characterized. In this study, the following genetic features for wheat development were addressed.

First, the micro RNA molecule TamiR1123 present in the Vrn-A1a promoter was found to be associated with the transcriptional level of Vrn-A1. Hence an alternative regulatory mechanism is proposed such that Vrn-A1 is regulated by plant age, low temperature, and short days through TamiR1123.

Second, the vernalization requirement duration in winter wheat was found to be controlled by TaVRN-A1 at the protein level. The mutation in the gene encoding TaVRN-A1 thus impacts its interaction ability with TaHOX1. This protein-protein interaction was confirmed by in vitro and in vivo assays. A SNP in the gene encoding TaHOX1 was associated with flowering time variation. This study presented the first example that MADS and HOX proteins involving homeosis have a direct-binding relationship in higher plants.

Third, TaHOX1 was mapped on chromosome 6B (TaHOX-B1), and homoeologues TaHOX-A1 and TaHOX-D1 were sequenced but showed no allelic variation. Whereas TaHOX-A2 was mapped on chromosome 2A due to an 18-bp indel polymorphism in exon 1, TaHOX-B2 or TaHOX-D2 showed no allelic variation.

Lastly a wheat centromeric protein encoded by TaCENPE1 from a yeast-2 hybrid (Y2H) library was also confirmed to directly bind with TaVRN1 in living cells based on a transient expression system applied in tobacco leaves. Plant height of TaCENPE1