NAC transcription factor: Difference between revisions
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The transcription regulatory region, generally lying at the highly diverged C-terminal, can either activate [20-22] or repress transcription [13,23,24]. Recently, the C-terminal of a novel NAC domain protein VNI have been shown to both activate and repress transcription [25]. More interestingly, VNI2 transcriptional repression motif can be transformed into the transcription activation domain under high salt conditions. It is therefore likely that the C-terminal domain isn’t only complex in sequence, but confer the multiple functions. Based on the sequence analyses, the transcription regulatory region has several group specific motifs that are rich in repeats of serine–threonine, proline–glutamine, or acidic residues, for example, the transcription regulatory region of rice NAC proteins was found to contain ten C-terminal motifs [27]. Another comprehensive study has revealed that these motifs are conserved for a given subgroup of NAC subfamilies but varies across the different subfamilies [2]. Thus, this region imparts variation to individual functions of NAC proteins. Additionally, because of the excessive low-complexity sequences, transcription regulatory regions have a high degree of intrinsic disorder (ID) and fail to have a single stable three-dimensional structure [28,29]. Such flexibility enables them to interact with different target proteins making them model proteins for systematic analysis of transcription factor functions and structural ID. Some NAC proteins have protein-binding ability in their TRRs [23,28,30]. An a-helical transmembrane (TM) motif present in some NAC proteins is responsible for plasma membrane or endoplasmic reticulum membrane anchoring [30]. Up to now, 18 membrane bound NAC proteins have been identified in Arabidopsis, 11 in soybean, seven in maize (Zea mays), six in grape, five each in rice, poplar, switchgrass (Panicum virgatum) and sorghum (Sorghum bicolor), and four in Medicago truncatula [31,32], which may play important regulatory roles under environmental cues. However, no VNDs and other NAC proteins relating to cell wall were identified to have transmembrane motif. | The transcription regulatory region, generally lying at the highly diverged C-terminal, can either activate [20-22] or repress transcription [13,23,24]. Recently, the C-terminal of a novel NAC domain protein VNI have been shown to both activate and repress transcription [25]. More interestingly, VNI2 transcriptional repression motif can be transformed into the transcription activation domain under high salt conditions. It is therefore likely that the C-terminal domain isn’t only complex in sequence, but confer the multiple functions. Based on the sequence analyses, the transcription regulatory region has several group specific motifs that are rich in repeats of serine–threonine, proline–glutamine, or acidic residues, for example, the transcription regulatory region of rice NAC proteins was found to contain ten C-terminal motifs [27]. Another comprehensive study has revealed that these motifs are conserved for a given subgroup of NAC subfamilies but varies across the different subfamilies [2]. Thus, this region imparts variation to individual functions of NAC proteins. Additionally, because of the excessive low-complexity sequences, transcription regulatory regions have a high degree of intrinsic disorder (ID) and fail to have a single stable three-dimensional structure [28,29]. Such flexibility enables them to interact with different target proteins making them model proteins for systematic analysis of transcription factor functions and structural ID. Some NAC proteins have protein-binding ability in their TRRs [23,28,30]. An a-helical transmembrane (TM) motif present in some NAC proteins is responsible for plasma membrane or endoplasmic reticulum membrane anchoring [30]. Up to now, 18 membrane bound NAC proteins have been identified in Arabidopsis, 11 in soybean, seven in maize (Zea mays), six in grape, five each in rice, poplar, switchgrass (Panicum virgatum) and sorghum (Sorghum bicolor), and four in Medicago truncatula [31,32], which may play important regulatory roles under environmental cues. However, no VNDs and other NAC proteins relating to cell wall were identified to have transmembrane motif. | ||
== The secondary cell wall biosynthesis switches == | |||
In vascular vessel, VND6 and VND7 control both secondary cell development and programmed cell death of vessels in both root and shoot tissues (1,33). The over-expression of VND6 and VND7 can induce ectopic differentiation of two different types of vessel elements: proto-xylem, and meta-xylem vessels. Reversely, the functional repression of VND6 and VND7 can inhibit vessel element formation. Additionally, the poplar VNDs can complement the Arabidopsis cell wall development defective mutant NST1NST3, suggesting that VNDs share the conserved functions with other secondary cell wall regulators [34]. | |||
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32. Kim, S.G. et al. (2010) Genome-scale screening and molecular characterization of membrane-bound transcription factors in Arabidopsis and rice. Genomics 95, 56–6 | 32. Kim, S.G. et al. (2010) Genome-scale screening and molecular characterization of membrane-bound transcription factors in Arabidopsis and rice. Genomics 95, 56–6 | ||
33. Yamaguchi, M. et al. (2008) Vascular -related NAC-domain 7 is involved in the differentiation of all types of xylem vessels in Arabidopsis roots and shoots. Plant J. 55,652-664 | |||
34. Zhong | |||
