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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.


Real-time expression profiles for 12 OsMLO genes. Anatomical samples were prepared from root (R), shoot (S), mature leaf (L), young panicle (3cm-YP), mature flower (MF), anther [uni- (AU), bi- (AB), and tricellular (AT)], and seed at 6 days after pollination (Se). Rice ubiquitin (OsUbi5) was served as internal control.
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Figure 2: Real-time expression profiles for 12 OsMLO genes. Anatomical samples were prepared from root (R), shoot (S), mature leaf (L), young panicle (3cm-YP), mature flower (MF), anther [uni- (AU), bi- (AB), and tricellular (AT)], and seed at 6 days after pollination (Se). Rice ubiquitin (OsUbi5) was served as internal control.

Mentions: To confirm the results from our meta-analysis of anatomical expression profiles, we performed real-time PCR with 12 rice MLO genes that are expressed in the roots, shoots, leaves, young panicles, mature flowers, and seeds (at 6 d post-pollination), as well as in anthers sampled at the uni-, bi-, and trinucleate stages (Figure 2). Our findings here closely matched those obtained from meta-analyses of tissue-specific expression profiles. However, we failed to detect any expression of OsMLO7, probably because its transcript level was extremely low. We determined that OsMLO11 was highly expressed in mature flowers and in uni-, bi-, and trinucleate anthers. These results demonstrated the high reliability of meta-expression profiles based on a large collection of transcriptome data.


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
Real-time expression profiles for 12 OsMLO genes. Anatomical samples were prepared from root (R), shoot (S), mature leaf (L), young panicle (3cm-YP), mature flower (MF), anther [uni- (AU), bi- (AB), and tricellular (AT)], and seed at 6 days after pollination (Se). Rice ubiquitin (OsUbi5) was served as internal control.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 2: Real-time expression profiles for 12 OsMLO genes. Anatomical samples were prepared from root (R), shoot (S), mature leaf (L), young panicle (3cm-YP), mature flower (MF), anther [uni- (AU), bi- (AB), and tricellular (AT)], and seed at 6 days after pollination (Se). Rice ubiquitin (OsUbi5) was served as internal control.
Mentions: To confirm the results from our meta-analysis of anatomical expression profiles, we performed real-time PCR with 12 rice MLO genes that are expressed in the roots, shoots, leaves, young panicles, mature flowers, and seeds (at 6 d post-pollination), as well as in anthers sampled at the uni-, bi-, and trinucleate stages (Figure 2). Our findings here closely matched those obtained from meta-analyses of tissue-specific expression profiles. However, we failed to detect any expression of OsMLO7, probably because its transcript level was extremely low. We determined that OsMLO11 was highly expressed in mature flowers and in uni-, bi-, and trinucleate anthers. These results demonstrated the high reliability of meta-expression profiles based on a large collection of transcriptome data.

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.