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A Systematic View of the MLO Family in Rice Suggests Their Novel Roles in Morphological Development, Diurnal Responses, the Light-Signaling Pathway, and Various Stress Responses

View Article: PubMed Central - PubMed

ABSTRACT

The Mildew resistance Locus O (MLO) family is unique to plants, containing genes that were initially identified as a susceptibility factor to powdery mildew pathogens. However, little is known about the roles and functional diversity of this family in rice, a model crop plant. The rice genome has 12 potential MLO family members. To achieve systematic functional assignments, we performed a phylogenomic analysis by integrating meta-expression data obtained from public sources of microarray data and real-time expression data into a phylogenic tree. Subsequently, we identified 12 MLO genes with various tissue-preferred patterns, including leaf, root, pollen, and ubiquitous expression. This suggested their functional diversity for morphological agronomic traits. We also used these integrated transcriptome data within a phylogenetic context to estimate the functional redundancy or specificity among OsMLO family members. Here, OsMLO12 showed preferential expression in mature pollen; OsMLO4, in the root tips; OsMLO10, throughout the roots except at the tips; and OsMLO8, expression preferential to the leaves and trinucleate pollen. Of particular interest to us was the diurnal expression of OsMLO1, OsMLO3, and OsMLO8, which indicated that they are potentially significant in responses to environmental changes. In osdxr mutants that show defects in the light response, OsMLO1, OsMLO3, OsMLO8, and four calmodulin genes were down-regulated. This finding provides insight into the novel functions of MLO proteins associated with the light-responsive methylerythritol 4-phosphate pathway. In addition, abiotic stress meta-expression data and real-time expression analysis implied that four and five MLO genes in rice are associated with responses to heat and cold stress, respectively. Upregulation of OsMLO3 by Magnaporthe oryzae infection further suggested that this gene participates in the response to pathogens. Our analysis has produced fundamental information that will enhance future studies of the diverse developmental or physiological phenomena mediated by the MLO family in this model plant system.

No MeSH data available.


Related in: MedlinePlus

Expression profiles of OsMLO genes under heat stress evaluated by real-time PCR analysis. OsHsp1 served as a positive marker for heat-stress response. OsUbi5 was used as internal control. M, control treatment; H, high-temperature treatment. Numbers after M and H indicate time points (hours) after stress treatment. **p < 0.01; *0.01 < p < 0.05.
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Figure 7: Expression profiles of OsMLO genes under heat stress evaluated by real-time PCR analysis. OsHsp1 served as a positive marker for heat-stress response. OsUbi5 was used as internal control. M, control treatment; H, high-temperature treatment. Numbers after M and H indicate time points (hours) after stress treatment. **p < 0.01; *0.01 < p < 0.05.

Mentions: Although the barley MLO genes are affected by abiotic stresses such as leaf-wounding and herbicides (Piffanelli et al., 2002), little is known about how genes in that family are influenced by other sources of stress. We used the log2 fold-change data in response to abiotic stresses (Figure S3) to investigate the meta-expression patterns of 12 rice MLO genes. Differential expression was monitored via real-time PCR with samples under either heat- or cold-stress conditions. As expected, OsMLO2, OsMLO3, OsMLO4, and OsMLO9 were rapidly up-regulated during the first 3 h of heat treatment (Figure 7). Their expression began to decline after 12 h of treatment but was still higher than that measured from the WT control. Among those four genes, OsMLO4 was the most responsive to high temperature, with expression being >30-fold higher than that in control plants after 6 h and remaining at that level for 12 h of treatment. Because OsMLO5, OsMLO6, and OsMLO7 were expressed only at low levels in the leaves, they were eliminated from further analysis of temperature sensitivity.


A Systematic View of the MLO Family in Rice Suggests Their Novel Roles in Morphological Development, Diurnal Responses, the Light-Signaling Pathway, and Various Stress Responses
Expression profiles of OsMLO genes under heat stress evaluated by real-time PCR analysis. OsHsp1 served as a positive marker for heat-stress response. OsUbi5 was used as internal control. M, control treatment; H, high-temperature treatment. Numbers after M and H indicate time points (hours) after stress treatment. **p < 0.01; *0.01 < p < 0.05.
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Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC5037229&req=5

Figure 7: Expression profiles of OsMLO genes under heat stress evaluated by real-time PCR analysis. OsHsp1 served as a positive marker for heat-stress response. OsUbi5 was used as internal control. M, control treatment; H, high-temperature treatment. Numbers after M and H indicate time points (hours) after stress treatment. **p < 0.01; *0.01 < p < 0.05.
Mentions: Although the barley MLO genes are affected by abiotic stresses such as leaf-wounding and herbicides (Piffanelli et al., 2002), little is known about how genes in that family are influenced by other sources of stress. We used the log2 fold-change data in response to abiotic stresses (Figure S3) to investigate the meta-expression patterns of 12 rice MLO genes. Differential expression was monitored via real-time PCR with samples under either heat- or cold-stress conditions. As expected, OsMLO2, OsMLO3, OsMLO4, and OsMLO9 were rapidly up-regulated during the first 3 h of heat treatment (Figure 7). Their expression began to decline after 12 h of treatment but was still higher than that measured from the WT control. Among those four genes, OsMLO4 was the most responsive to high temperature, with expression being >30-fold higher than that in control plants after 6 h and remaining at that level for 12 h of treatment. Because OsMLO5, OsMLO6, and OsMLO7 were expressed only at low levels in the leaves, they were eliminated from further analysis of temperature sensitivity.

View Article: PubMed Central - PubMed

ABSTRACT

The Mildew resistance Locus O (MLO) family is unique to plants, containing genes that were initially identified as a susceptibility factor to powdery mildew pathogens. However, little is known about the roles and functional diversity of this family in rice, a model crop plant. The rice genome has 12 potential MLO family members. To achieve systematic functional assignments, we performed a phylogenomic analysis by integrating meta-expression data obtained from public sources of microarray data and real-time expression data into a phylogenic tree. Subsequently, we identified 12 MLO genes with various tissue-preferred patterns, including leaf, root, pollen, and ubiquitous expression. This suggested their functional diversity for morphological agronomic traits. We also used these integrated transcriptome data within a phylogenetic context to estimate the functional redundancy or specificity among OsMLO family members. Here, OsMLO12 showed preferential expression in mature pollen; OsMLO4, in the root tips; OsMLO10, throughout the roots except at the tips; and OsMLO8, expression preferential to the leaves and trinucleate pollen. Of particular interest to us was the diurnal expression of OsMLO1, OsMLO3, and OsMLO8, which indicated that they are potentially significant in responses to environmental changes. In osdxr mutants that show defects in the light response, OsMLO1, OsMLO3, OsMLO8, and four calmodulin genes were down-regulated. This finding provides insight into the novel functions of MLO proteins associated with the light-responsive methylerythritol 4-phosphate pathway. In addition, abiotic stress meta-expression data and real-time expression analysis implied that four and five MLO genes in rice are associated with responses to heat and cold stress, respectively. Upregulation of OsMLO3 by Magnaporthe oryzae infection further suggested that this gene participates in the response to pathogens. Our analysis has produced fundamental information that will enhance future studies of the diverse developmental or physiological phenomena mediated by the MLO family in this model plant system.

No MeSH data available.


Related in: MedlinePlus