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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.


Comparisons of expression patterns among OsMLO genes. Log2 intensity values (colored by species) ranged from 5 to 15: Arabidopsis thaliana (blue to yellow), Oryza sativa (green to red), and Hordeum vulgare (cerulean to violet). OsMLO11 expression pattern was not available in Genevestigator data. Clade number is indicated on left side of phylogenetic tree.
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Figure 3: Comparisons of expression patterns among OsMLO genes. Log2 intensity values (colored by species) ranged from 5 to 15: Arabidopsis thaliana (blue to yellow), Oryza sativa (green to red), and Hordeum vulgare (cerulean to violet). OsMLO11 expression pattern was not available in Genevestigator data. Clade number is indicated on left side of phylogenetic tree.

Mentions: Our phylogenetic tree covered 29 protein sequences that were aligned from rice (12 MLOs), Arabidopsis (15), and barley (2). This established four clades, i.e., I through IV (Figure 3). Dividing the number of clade for MLO family has yet to be unanimous (Feechan et al., 2008; Pessina et al., 2014; Kusch et al., 2016), we separated 29 MLOs into four clades base on primary evolution and relative known function gene with small numbers of MLO genes. This tree implied that the evolutionary processes for MLO genes from monocots and dicots were rather independent. For example, the 29 members included only two orthologous pairings—AtMLO4/OsMLO11 in Clade III and OsMLO10/HvMLO3 in Clade IV.


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
Comparisons of expression patterns among OsMLO genes. Log2 intensity values (colored by species) ranged from 5 to 15: Arabidopsis thaliana (blue to yellow), Oryza sativa (green to red), and Hordeum vulgare (cerulean to violet). OsMLO11 expression pattern was not available in Genevestigator data. Clade number is indicated on left side of phylogenetic tree.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 3: Comparisons of expression patterns among OsMLO genes. Log2 intensity values (colored by species) ranged from 5 to 15: Arabidopsis thaliana (blue to yellow), Oryza sativa (green to red), and Hordeum vulgare (cerulean to violet). OsMLO11 expression pattern was not available in Genevestigator data. Clade number is indicated on left side of phylogenetic tree.
Mentions: Our phylogenetic tree covered 29 protein sequences that were aligned from rice (12 MLOs), Arabidopsis (15), and barley (2). This established four clades, i.e., I through IV (Figure 3). Dividing the number of clade for MLO family has yet to be unanimous (Feechan et al., 2008; Pessina et al., 2014; Kusch et al., 2016), we separated 29 MLOs into four clades base on primary evolution and relative known function gene with small numbers of MLO genes. This tree implied that the evolutionary processes for MLO genes from monocots and dicots were rather independent. For example, the 29 members included only two orthologous pairings—AtMLO4/OsMLO11 in Clade III and OsMLO10/HvMLO3 in Clade IV.

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.