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The dynamics of soybean leaf and shoot apical meristem transcriptome undergoing floral initiation process.

Wong CE, Singh MB, Bhalla PL - PLoS ONE (2013)

Bottom Line: A total of 2951 shoot apical meristem and 13,609 leaf sequences with significant profile changes during the time course examined were identified.Transcripts associated with protein degradation were also significantly changing in leaf and SAM implicating their involvement in triggering the developmental switch.Further, evidence is emerging that the conversion of shoot apical meristem to inflorescence meristem is linked with the interplay of auxin, cytokinin and GA creating a low cytokinin and high GA environment.

View Article: PubMed Central - PubMed

Affiliation: Plant Molecular Biology and Biotechnology Group, ARC Centre of Excellence for Integrative Legume Research, Melbourne School of Land and Environment, The University of Melbourne, Parkville, Victoria, Australia.

ABSTRACT
Flowering process governs seed set and thus affects agricultural productivity. Soybean, a major legume crop, requires short-day photoperiod conditions for flowering. While leaf-derived signal(s) are essential for the photoperiod-induced floral initiation process at the shoot apical meristem, molecular events associated with early floral transition stages in either leaves or shoot apical meristems are not well understood. To provide novel insights into the molecular basis of floral initiation, RNA-Seq was used to characterize the soybean transcriptome of leaf and micro-dissected shoot apical meristem at different time points after short-day treatment. Shoot apical meristem expressed a higher number of transcripts in comparison to that of leaf highlighting greater diversity and abundance of transcripts expressed in the shoot apical meristem. A total of 2951 shoot apical meristem and 13,609 leaf sequences with significant profile changes during the time course examined were identified. Most changes in mRNA level occurred after 1short-day treatment. Transcripts involved in mediating responses to stimulus including hormones or in various metabolic processes represent the top enriched GO functional category for the SAM and leaf dataset, respectively. Transcripts associated with protein degradation were also significantly changing in leaf and SAM implicating their involvement in triggering the developmental switch. RNA-Seq analysis of shoot apical meristem and leaf from soybean undergoing floral transition reveal major reprogramming events in leaves and the SAM that point toward hormones gibberellins (GA) and cytokinin as key regulators in the production of systemic flowering signal(s) in leaves. These hormones may form part of the systemic signals in addition to the established florigen, FLOWERING LOCUS T (FT). Further, evidence is emerging that the conversion of shoot apical meristem to inflorescence meristem is linked with the interplay of auxin, cytokinin and GA creating a low cytokinin and high GA environment.

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The floral initiation process in soybean.A. An overview of short-day responsive processes in leaf and SAM of soybean. Functional groups of transcripts largely up- or down- regulated are depicted schematically as red or green boxes, respectively while those containing both up- or down-regulated sequences are represented in yellow box. A complete list of Mapman significantly enriched functional categories is given in Table S2. B. A hypothetical model illustrating potential molecular events underlying the floral initiation process in soybean with an emphasis on hormonal regulation. The model shows the action of auxin, cytokinin (CK) and GA in concert with other known factors (described in Results and Discussion) in regulating the developmental transition in soybean. In particular, GA and CK may form part of the systemic signals in addition to FT. The induction of CKX possibly via auxin to breakdown cytokinin is likely to create a low cytokinin and high GA environment triggering the conversion of SAM to inflorescence meristem.
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pone-0065319-g008: The floral initiation process in soybean.A. An overview of short-day responsive processes in leaf and SAM of soybean. Functional groups of transcripts largely up- or down- regulated are depicted schematically as red or green boxes, respectively while those containing both up- or down-regulated sequences are represented in yellow box. A complete list of Mapman significantly enriched functional categories is given in Table S2. B. A hypothetical model illustrating potential molecular events underlying the floral initiation process in soybean with an emphasis on hormonal regulation. The model shows the action of auxin, cytokinin (CK) and GA in concert with other known factors (described in Results and Discussion) in regulating the developmental transition in soybean. In particular, GA and CK may form part of the systemic signals in addition to FT. The induction of CKX possibly via auxin to breakdown cytokinin is likely to create a low cytokinin and high GA environment triggering the conversion of SAM to inflorescence meristem.

Mentions: Representatives of significantly enriched functional groups as deduced from Mapman and AgriGO analysis over the time course of the short-day treatment is summarized in Figure 8A. Rapid sensing and signaling of the change in photoperiod likely involves various leaf transcripts in ‘signaling’ and ‘transcription factor’ categories. As sugar is known not only as fuels but also as signaling molecules, sequences in carbohydrate metabolism could also serve similar signaling roles. In response to the signaling events, major reprogramming occurs in both leaves and the SAM as evident by a great number of transcripts differentially expressed in the ‘protein synthesis and degradation’ category. This ultimately leads to the induction of various MADS-box transcription factors in the SAM from 3-short-day onwards.


The dynamics of soybean leaf and shoot apical meristem transcriptome undergoing floral initiation process.

Wong CE, Singh MB, Bhalla PL - PLoS ONE (2013)

The floral initiation process in soybean.A. An overview of short-day responsive processes in leaf and SAM of soybean. Functional groups of transcripts largely up- or down- regulated are depicted schematically as red or green boxes, respectively while those containing both up- or down-regulated sequences are represented in yellow box. A complete list of Mapman significantly enriched functional categories is given in Table S2. B. A hypothetical model illustrating potential molecular events underlying the floral initiation process in soybean with an emphasis on hormonal regulation. The model shows the action of auxin, cytokinin (CK) and GA in concert with other known factors (described in Results and Discussion) in regulating the developmental transition in soybean. In particular, GA and CK may form part of the systemic signals in addition to FT. The induction of CKX possibly via auxin to breakdown cytokinin is likely to create a low cytokinin and high GA environment triggering the conversion of SAM to inflorescence meristem.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3675103&req=5

pone-0065319-g008: The floral initiation process in soybean.A. An overview of short-day responsive processes in leaf and SAM of soybean. Functional groups of transcripts largely up- or down- regulated are depicted schematically as red or green boxes, respectively while those containing both up- or down-regulated sequences are represented in yellow box. A complete list of Mapman significantly enriched functional categories is given in Table S2. B. A hypothetical model illustrating potential molecular events underlying the floral initiation process in soybean with an emphasis on hormonal regulation. The model shows the action of auxin, cytokinin (CK) and GA in concert with other known factors (described in Results and Discussion) in regulating the developmental transition in soybean. In particular, GA and CK may form part of the systemic signals in addition to FT. The induction of CKX possibly via auxin to breakdown cytokinin is likely to create a low cytokinin and high GA environment triggering the conversion of SAM to inflorescence meristem.
Mentions: Representatives of significantly enriched functional groups as deduced from Mapman and AgriGO analysis over the time course of the short-day treatment is summarized in Figure 8A. Rapid sensing and signaling of the change in photoperiod likely involves various leaf transcripts in ‘signaling’ and ‘transcription factor’ categories. As sugar is known not only as fuels but also as signaling molecules, sequences in carbohydrate metabolism could also serve similar signaling roles. In response to the signaling events, major reprogramming occurs in both leaves and the SAM as evident by a great number of transcripts differentially expressed in the ‘protein synthesis and degradation’ category. This ultimately leads to the induction of various MADS-box transcription factors in the SAM from 3-short-day onwards.

Bottom Line: A total of 2951 shoot apical meristem and 13,609 leaf sequences with significant profile changes during the time course examined were identified.Transcripts associated with protein degradation were also significantly changing in leaf and SAM implicating their involvement in triggering the developmental switch.Further, evidence is emerging that the conversion of shoot apical meristem to inflorescence meristem is linked with the interplay of auxin, cytokinin and GA creating a low cytokinin and high GA environment.

View Article: PubMed Central - PubMed

Affiliation: Plant Molecular Biology and Biotechnology Group, ARC Centre of Excellence for Integrative Legume Research, Melbourne School of Land and Environment, The University of Melbourne, Parkville, Victoria, Australia.

ABSTRACT
Flowering process governs seed set and thus affects agricultural productivity. Soybean, a major legume crop, requires short-day photoperiod conditions for flowering. While leaf-derived signal(s) are essential for the photoperiod-induced floral initiation process at the shoot apical meristem, molecular events associated with early floral transition stages in either leaves or shoot apical meristems are not well understood. To provide novel insights into the molecular basis of floral initiation, RNA-Seq was used to characterize the soybean transcriptome of leaf and micro-dissected shoot apical meristem at different time points after short-day treatment. Shoot apical meristem expressed a higher number of transcripts in comparison to that of leaf highlighting greater diversity and abundance of transcripts expressed in the shoot apical meristem. A total of 2951 shoot apical meristem and 13,609 leaf sequences with significant profile changes during the time course examined were identified. Most changes in mRNA level occurred after 1short-day treatment. Transcripts involved in mediating responses to stimulus including hormones or in various metabolic processes represent the top enriched GO functional category for the SAM and leaf dataset, respectively. Transcripts associated with protein degradation were also significantly changing in leaf and SAM implicating their involvement in triggering the developmental switch. RNA-Seq analysis of shoot apical meristem and leaf from soybean undergoing floral transition reveal major reprogramming events in leaves and the SAM that point toward hormones gibberellins (GA) and cytokinin as key regulators in the production of systemic flowering signal(s) in leaves. These hormones may form part of the systemic signals in addition to the established florigen, FLOWERING LOCUS T (FT). Further, evidence is emerging that the conversion of shoot apical meristem to inflorescence meristem is linked with the interplay of auxin, cytokinin and GA creating a low cytokinin and high GA environment.

Show MeSH
Related in: MedlinePlus