Differential gene expression patterns in leaves between hybrids and their parental inbreds are correlated with heterosis in a wheat diallel cross

Abstract

In spite of commercial use of heterosis in agriculture, the molecular basis of heterosis is poorly understood. Improved differential display was used in this study to analyze alterations in gene expression between hybrid and parents in leaves at jointing stage and heading stage in a wheat diallel cross involving 20 hybrids and nine parents, with the purpose of determining the relationship of differential expression patterns with heterosis in nine agronomic traits. About 2800 fragments were displayed from each hybrid and its parents, among which about 30% were differentially expressed between hybrids and their parents. Four patterns of differential expression were observed: (i) fragments observed in both parents but not in F 1 (BPnF 1); (ii) fragments that occurred in either of the parents but not in F 1 (UPnF 1); (iii) fragments observed only in F 1 but not in either of the parents (F 1nBP); (iv) fragments present in one of the parents and F 1 (UPF 1). UPnF 1 pattern is negatively correlated with heterosis in seven traits, while F 1nBP pattern is positively correlated with heterosis in six traits, and UPF 1 pattern is positively correlated with heterosis in three traits. BPnF 1 is not correlated with heterosis in any of the nine traits. We conclude that these differentially expressed genes, though functionally not known yet, play an important role for hybrids to demonstrate heterosis.