Abstract
In spite of commercial use of heterosis in agriculture, the molecular basis of heterosis is poorly understood. It was observed that maize hybrid Zong3/87-1 exhibited an earlier onset or heterosis in radicle emergence. To get insights into the underlying mechanism of heterosis in radicle emergence, differential proteomic analysis between hybrid and its parental lines was performed. In total, the number of differentially expressed protein spots between hybrid and its parental lines in dry and 24 h imbibed seed embryos were 134 and 191, respectively, among which 47.01% (63/134) and 34.55% (66/191) protein spots displayed nonadditively expressed pattern. Remarkably, 54.55% of nonadditively accumulated proteins in 24 h imbibed seed embryos displayed above or equal to the level of the higher parent patterns. Moreover, 155 differentially expressed protein spots were identified, which were grouped into eight functional classes, including transcription & translation, energy & metabolism, signal transduction, disease & defense, storage protein, transposable element, cell growth & division and unclassified proteins. In addition, one of the upregulated proteins in F1 hybrids was ZmACT2, a homolog of Arabidopsis thaliana ACT7 (AtACT7). Expressing ZmACT2 driven by the AtACT7 promoter partially complemented the low germination phenotype in the Atact7 mutant. These results indicated that hybridization between two parental lines can cause changes in the expression of a variety of proteins, and it is concluded that the altered pattern of gene expression at translational level in the hybrid may be responsible for the observed heterosis.
Highlights
Heterosis or hybrid vigor was defined as the advantage of hybrid performance over its parents in terms of biomass, size, yield, speeds of development, fertility, resistance to biotic and abiotic stresses
At the level of gene expression, complex transcriptional networks specific for different developmental stages and tissues in maize, wheat, rice and Arabidopsis were monitored, and these results indicated that hybridization between two parental lines could cause expression changes of different genes, which might be responsible for the observed heterosis [3,4,5,6,7,8,9,10]
It can be concluded that the altered pattern of ZmACT2 gene expression at translational level in the hybrid may be responsible for the observed heterosis
Summary
Heterosis or hybrid vigor was defined as the advantage of hybrid performance over its parents in terms of biomass, size, yield, speeds of development, fertility, resistance to biotic and abiotic stresses. Comparative proteomic analysis of 25 and 35 DAP (days after pollination) seed embryos of maize reciprocal F1-hybrids and their parental inbred lines revealed that 141 proteins exhibited nonadditive accumulation in at least one hybrid and approximately 44% of differently expressed proteins displayed low-dominant in hybrid [17]. Taken together, these observations at translational level add circumstantial evidence that expression differences between hybrid and its parental lines exist at mRNA levels, and at protein abundances
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