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Involvements of PCD and changes in gene expression profile during self-pruning of spring shoots in sweet orange (Citrus sinensis).

Zhang JZ, Zhao K, Ai XY, Hu CG - BMC Genomics (2014)

Bottom Line: Some genes were related to PCD, while others were associated with cell wall biosynthesis or metabolism.These results strongly suggest that abscission layers activate both catabolic and anabolic wall modification pathways during the self-pruning process.Based on these findings, a model for sweet orange spring shoot self-pruning is proposed, which will enable us to better understand the mechanism of self-pruning and abscission.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Horticultural Plant Biology (Ministry of Education), College of Horticulture and Forestry Science, Huazhong Agricultural University, Wuhan, 430070, China. chungen@mail.hzau.edu.cn.

ABSTRACT

Background: Citrus shoot tips abscise at an anatomically distinct abscission zone (AZ) that separates the top part of the shoots into basal and apical portions (citrus self-pruning). Cell separation occurs only at the AZ, which suggests its cells have distinctive molecular regulation. Although several studies have looked into the morphological aspects of self-pruning process, the underlying molecular mechanisms remain unknown.

Results: In this study, the hallmarks of programmed cell death (PCD) were identified by TUNEL experiments, transmission electron microscopy (TEM) and histochemical staining for reactive oxygen species (ROS) during self-pruning of the spring shoots in sweet orange. Our results indicated that PCD occurred systematically and progressively and may play an important role in the control of self-pruning of citrus. Microarray analysis was used to examine transcriptome changes at three stages of self-pruning, and 1,378 differentially expressed genes were identified. Some genes were related to PCD, while others were associated with cell wall biosynthesis or metabolism. These results strongly suggest that abscission layers activate both catabolic and anabolic wall modification pathways during the self-pruning process. In addition, a strong correlation was observed between self-pruning and the expression of hormone-related genes. Self-pruning plays an important role in citrus floral bud initiation. Therefore, several key flowering homologs of Arabidopsis and tomato shoot apical meristem (SAM) activity genes were investigated in sweet orange by real-time PCR and in situ hybridization, and the results indicated that these genes were preferentially expressed in SAM as well as axillary meristem.

Conclusion: Based on these findings, a model for sweet orange spring shoot self-pruning is proposed, which will enable us to better understand the mechanism of self-pruning and abscission.

Show MeSH
Expression patterns of DEGs. (A) The total numbers of DEGs (fold changes ≥ 4, 6, and 8; p ≤ 0.001) at stage 1, stage 2 and stage 3. (B) Venn diagram showing the overlapping of DEGs at three development stages. (C) Cluster 1 consisting of 571 DEGs; (D) Cluster 2 consisting of 337 DEGs; (E) Cluster 3 consisting of 335 DEGs; (F) Cluster 4 consisting of 135 DEGs.
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Fig5: Expression patterns of DEGs. (A) The total numbers of DEGs (fold changes ≥ 4, 6, and 8; p ≤ 0.001) at stage 1, stage 2 and stage 3. (B) Venn diagram showing the overlapping of DEGs at three development stages. (C) Cluster 1 consisting of 571 DEGs; (D) Cluster 2 consisting of 337 DEGs; (E) Cluster 3 consisting of 335 DEGs; (F) Cluster 4 consisting of 135 DEGs.

Mentions: To identify DEGs during the self-pruning process, a citrus microarray was used to measure the expression of genes at three stages. Among the three stages, more genes were up-regulated (15,764) than down-regulated (14,631) from stage 1 to stage 2. However, more genes were down-regulated (16,279) than up-regulated (14,116) from stage 1 to stage 3. A total of 154 DEGs were identified from stage 1 to stage 2 based on P ≤ 0.001 and four fold changes. Among these DEGs, 30 genes were up-regulated and 124 were down-regulated (Figure 5A). In addition, 1,306 DEGs were identified from stage 1 to stage 3, with 837 genes up-regulated and 469 down-regulated (Figure 5A). Combining the results obtained for the three stages, 1,378 DEGs were identified as candidate self-pruning-related genes; a total of 82 DEGs were in common to all three stages and may represent typical self-pruning responsive genes (Figure 5B).


Involvements of PCD and changes in gene expression profile during self-pruning of spring shoots in sweet orange (Citrus sinensis).

Zhang JZ, Zhao K, Ai XY, Hu CG - BMC Genomics (2014)

Expression patterns of DEGs. (A) The total numbers of DEGs (fold changes ≥ 4, 6, and 8; p ≤ 0.001) at stage 1, stage 2 and stage 3. (B) Venn diagram showing the overlapping of DEGs at three development stages. (C) Cluster 1 consisting of 571 DEGs; (D) Cluster 2 consisting of 337 DEGs; (E) Cluster 3 consisting of 335 DEGs; (F) Cluster 4 consisting of 135 DEGs.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4209071&req=5

Fig5: Expression patterns of DEGs. (A) The total numbers of DEGs (fold changes ≥ 4, 6, and 8; p ≤ 0.001) at stage 1, stage 2 and stage 3. (B) Venn diagram showing the overlapping of DEGs at three development stages. (C) Cluster 1 consisting of 571 DEGs; (D) Cluster 2 consisting of 337 DEGs; (E) Cluster 3 consisting of 335 DEGs; (F) Cluster 4 consisting of 135 DEGs.
Mentions: To identify DEGs during the self-pruning process, a citrus microarray was used to measure the expression of genes at three stages. Among the three stages, more genes were up-regulated (15,764) than down-regulated (14,631) from stage 1 to stage 2. However, more genes were down-regulated (16,279) than up-regulated (14,116) from stage 1 to stage 3. A total of 154 DEGs were identified from stage 1 to stage 2 based on P ≤ 0.001 and four fold changes. Among these DEGs, 30 genes were up-regulated and 124 were down-regulated (Figure 5A). In addition, 1,306 DEGs were identified from stage 1 to stage 3, with 837 genes up-regulated and 469 down-regulated (Figure 5A). Combining the results obtained for the three stages, 1,378 DEGs were identified as candidate self-pruning-related genes; a total of 82 DEGs were in common to all three stages and may represent typical self-pruning responsive genes (Figure 5B).

Bottom Line: Some genes were related to PCD, while others were associated with cell wall biosynthesis or metabolism.These results strongly suggest that abscission layers activate both catabolic and anabolic wall modification pathways during the self-pruning process.Based on these findings, a model for sweet orange spring shoot self-pruning is proposed, which will enable us to better understand the mechanism of self-pruning and abscission.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Horticultural Plant Biology (Ministry of Education), College of Horticulture and Forestry Science, Huazhong Agricultural University, Wuhan, 430070, China. chungen@mail.hzau.edu.cn.

ABSTRACT

Background: Citrus shoot tips abscise at an anatomically distinct abscission zone (AZ) that separates the top part of the shoots into basal and apical portions (citrus self-pruning). Cell separation occurs only at the AZ, which suggests its cells have distinctive molecular regulation. Although several studies have looked into the morphological aspects of self-pruning process, the underlying molecular mechanisms remain unknown.

Results: In this study, the hallmarks of programmed cell death (PCD) were identified by TUNEL experiments, transmission electron microscopy (TEM) and histochemical staining for reactive oxygen species (ROS) during self-pruning of the spring shoots in sweet orange. Our results indicated that PCD occurred systematically and progressively and may play an important role in the control of self-pruning of citrus. Microarray analysis was used to examine transcriptome changes at three stages of self-pruning, and 1,378 differentially expressed genes were identified. Some genes were related to PCD, while others were associated with cell wall biosynthesis or metabolism. These results strongly suggest that abscission layers activate both catabolic and anabolic wall modification pathways during the self-pruning process. In addition, a strong correlation was observed between self-pruning and the expression of hormone-related genes. Self-pruning plays an important role in citrus floral bud initiation. Therefore, several key flowering homologs of Arabidopsis and tomato shoot apical meristem (SAM) activity genes were investigated in sweet orange by real-time PCR and in situ hybridization, and the results indicated that these genes were preferentially expressed in SAM as well as axillary meristem.

Conclusion: Based on these findings, a model for sweet orange spring shoot self-pruning is proposed, which will enable us to better understand the mechanism of self-pruning and abscission.

Show MeSH