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Gene expression analyses in maize inbreds and hybrids with varying levels of heterosis.

Stupar RM, Gardiner JM, Oldre AG, Haun WJ, Chandler VL, Springer NM - BMC Plant Biol. (2008)

Bottom Line: We have found that maize inbred genetic diversity is correlated with transcriptional variation.These findings suggest that heterosis is probably not a consequence of higher levels of additive or non-additive expression, but may be related to transcriptional variation between parents.The lack of correlation between better parent heterosis levels for different traits suggests that transcriptional diversity at specific sets of genes may influence heterosis for different traits.

View Article: PubMed Central - HTML - PubMed

Affiliation: Center for Plant and Microbial Genomics, Department of Plant Biology, University of Minnesota, Saint Paul MN 55108, USA. stup0004@umn.edu

ABSTRACT

Background: Heterosis is the superior performance of F1 hybrid progeny relative to the parental phenotypes. Maize exhibits heterosis for a wide range of traits, however the magnitude of heterosis is highly variable depending on the choice of parents and the trait(s) measured. We have used expression profiling to determine whether the level, or types, of non-additive gene expression vary in maize hybrids with different levels of genetic diversity or heterosis.

Results: We observed that the distributions of better parent heterosis among a series of 25 maize hybrids generally do not exhibit significant correlations between different traits. Expression profiling analyses for six of these hybrids, chosen to represent diversity in genotypes and heterosis responses, revealed a correlation between genetic diversity and transcriptional variation. The majority of differentially expressed genes in each of the six different hybrids exhibited additive expression patterns, and approximately 25% exhibited statistically significant non-additive expression profiles. Among the non-additive profiles, approximately 80% exhibited hybrid expression levels between the parental levels, approximately 20% exhibited hybrid expression levels at the parental levels and ~1% exhibited hybrid levels outside the parental range.

Conclusion: We have found that maize inbred genetic diversity is correlated with transcriptional variation. However, sampling of seedling tissues indicated that the frequencies of additive and non-additive expression patterns are very similar across a range of hybrid lines. These findings suggest that heterosis is probably not a consequence of higher levels of additive or non-additive expression, but may be related to transcriptional variation between parents. The lack of correlation between better parent heterosis levels for different traits suggests that transcriptional diversity at specific sets of genes may influence heterosis for different traits.

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Heterosis for non-yield traits. The percent BPH is shown for all traits and all hybrids scored in this study. The numerical BPH values are available in Additional file 2. Red bars represent BPH for hybrids generated between SS and NSS inbreds, blue bars represent BPH for hybrids generated within SS and NSS inbreds, and grey bars represent BPH for hybrids derived from an inbred line with mixed origin (F2).
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Figure 2: Heterosis for non-yield traits. The percent BPH is shown for all traits and all hybrids scored in this study. The numerical BPH values are available in Additional file 2. Red bars represent BPH for hybrids generated between SS and NSS inbreds, blue bars represent BPH for hybrids generated within SS and NSS inbreds, and grey bars represent BPH for hybrids derived from an inbred line with mixed origin (F2).

Mentions: We measured the mature plant height, 50-seed weight, days to flowering, seedling plant height and seedling biomass BPH levels for a series of hybrids. The inbred lines B73 or Mo17 were used as paternal parents in all hybrids studied. The phenotypic values for each replicate of all five traits are provided in Additional file 1 and the BPH values are available in Figure 1 and Additional file 2. The relative BPH levels were quite variable among the different traits (Figure 2). For example, Oh43 × B73 exhibited the highest BPH for seed weight, but the fifth lowest BPH for days to flowering (Figure 2; see Additional file 2). We tested whether there was a correlation in the level of BPH among hybrids for any two traits [see Additional file 3]. Seedling height and seedling biomass exhibited a strong correlation (p < 0.0001) while plant height and days to flowering exhibited a weaker, but significant, correlation (p = 0.013). The other eight trait comparisons did not show significant correlations. Thus, in general, the level of BPH heterosis for one trait is a poor predictor of the level of heterosis for another trait.


Gene expression analyses in maize inbreds and hybrids with varying levels of heterosis.

Stupar RM, Gardiner JM, Oldre AG, Haun WJ, Chandler VL, Springer NM - BMC Plant Biol. (2008)

Heterosis for non-yield traits. The percent BPH is shown for all traits and all hybrids scored in this study. The numerical BPH values are available in Additional file 2. Red bars represent BPH for hybrids generated between SS and NSS inbreds, blue bars represent BPH for hybrids generated within SS and NSS inbreds, and grey bars represent BPH for hybrids derived from an inbred line with mixed origin (F2).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2365949&req=5

Figure 2: Heterosis for non-yield traits. The percent BPH is shown for all traits and all hybrids scored in this study. The numerical BPH values are available in Additional file 2. Red bars represent BPH for hybrids generated between SS and NSS inbreds, blue bars represent BPH for hybrids generated within SS and NSS inbreds, and grey bars represent BPH for hybrids derived from an inbred line with mixed origin (F2).
Mentions: We measured the mature plant height, 50-seed weight, days to flowering, seedling plant height and seedling biomass BPH levels for a series of hybrids. The inbred lines B73 or Mo17 were used as paternal parents in all hybrids studied. The phenotypic values for each replicate of all five traits are provided in Additional file 1 and the BPH values are available in Figure 1 and Additional file 2. The relative BPH levels were quite variable among the different traits (Figure 2). For example, Oh43 × B73 exhibited the highest BPH for seed weight, but the fifth lowest BPH for days to flowering (Figure 2; see Additional file 2). We tested whether there was a correlation in the level of BPH among hybrids for any two traits [see Additional file 3]. Seedling height and seedling biomass exhibited a strong correlation (p < 0.0001) while plant height and days to flowering exhibited a weaker, but significant, correlation (p = 0.013). The other eight trait comparisons did not show significant correlations. Thus, in general, the level of BPH heterosis for one trait is a poor predictor of the level of heterosis for another trait.

Bottom Line: We have found that maize inbred genetic diversity is correlated with transcriptional variation.These findings suggest that heterosis is probably not a consequence of higher levels of additive or non-additive expression, but may be related to transcriptional variation between parents.The lack of correlation between better parent heterosis levels for different traits suggests that transcriptional diversity at specific sets of genes may influence heterosis for different traits.

View Article: PubMed Central - HTML - PubMed

Affiliation: Center for Plant and Microbial Genomics, Department of Plant Biology, University of Minnesota, Saint Paul MN 55108, USA. stup0004@umn.edu

ABSTRACT

Background: Heterosis is the superior performance of F1 hybrid progeny relative to the parental phenotypes. Maize exhibits heterosis for a wide range of traits, however the magnitude of heterosis is highly variable depending on the choice of parents and the trait(s) measured. We have used expression profiling to determine whether the level, or types, of non-additive gene expression vary in maize hybrids with different levels of genetic diversity or heterosis.

Results: We observed that the distributions of better parent heterosis among a series of 25 maize hybrids generally do not exhibit significant correlations between different traits. Expression profiling analyses for six of these hybrids, chosen to represent diversity in genotypes and heterosis responses, revealed a correlation between genetic diversity and transcriptional variation. The majority of differentially expressed genes in each of the six different hybrids exhibited additive expression patterns, and approximately 25% exhibited statistically significant non-additive expression profiles. Among the non-additive profiles, approximately 80% exhibited hybrid expression levels between the parental levels, approximately 20% exhibited hybrid expression levels at the parental levels and ~1% exhibited hybrid levels outside the parental range.

Conclusion: We have found that maize inbred genetic diversity is correlated with transcriptional variation. However, sampling of seedling tissues indicated that the frequencies of additive and non-additive expression patterns are very similar across a range of hybrid lines. These findings suggest that heterosis is probably not a consequence of higher levels of additive or non-additive expression, but may be related to transcriptional variation between parents. The lack of correlation between better parent heterosis levels for different traits suggests that transcriptional diversity at specific sets of genes may influence heterosis for different traits.

Show MeSH