Abstract
Moderate leaf rolling is beneficial for leaf erectness and compact plant architecture. However, our understanding regarding the molecular mechanisms of leaf rolling is still limited. Here, we characterized a semi-dominant rice (Oryza sativa L.) mutant upward rolled leaf 1 (Url1) showing adaxially rolled leaves due to a decrease in the number and size of bulliform cells. Map-based cloning revealed that URL1 encodes the homeodomain-leucine zipper (HD-Zip) IV family member RICE OUTERMOST CELL-SPECIFIC 8 (ROC8). A single-base substitution in one of the two conserved complementary motifs unique to the 3′-untranslated region of this family enhanced URL1 mRNA stability and abundance in the Url1 mutant. URL1 (UPWARD ROLLED LEAF1) contains an ethylene-responsive element binding factor-associated amphiphilic repression motif and functions as a transcriptional repressor via interaction with the TOPLESS co-repressor OsTPL2. Rather than homodimerizing, URL1 heterodimerizes with another HD-ZIP IV member ROC5. URL1 could bind directly to the promoter and suppress the expression of abaxially curled leaf 1 (ACL1), a positive regulator of bulliform cell development. Knockout of OsTPL2 or ROC5 or overexpression of ACL1 in the Url1 mutant partially suppressed the leaf-rolling phenotype. Our results reveal a regulatory network whereby a transcriptional repression complex composed of URL1, ROC5, and the transcriptional corepressor TPL2 suppresses the expression of the ACL1 gene, thus modulating bulliform cell development and leaf rolling in rice.
Highlights
Leaf size and shape are important components of plant architecture (Li et al, 2010)
The F1 plants derived from a cross between upward rolled leaf 1 (Url1) and wild type (WT) had semi-rolled leaves, an intermediate between the flat and fully rolled leaves of the homozygous parental plants (Figure 1, A and C)
The results showed that there was no significant difference in nascent transcription between WT and the Url1 mutant (Figure 3E), suggesting that the C679T mutation did not affect nascent transcription and that URL1 mRNA levels may analysis of the URL1 mRNA transcript level in the Url1 mutant and WT using primer sets URL1-I, URL1-II, and URL1-III located in different regions of URL1, respectively
Summary
Leaf size and shape are important components of plant architecture (Li et al, 2010). Appropriate leaf rolling maximizes light capture and reduces transpiration under dry conditions (Lang et al, 2004; Moon and Hake, 2011). Several rice (Oryza sativa L.) genes have been identified to regulate abaxial or adaxial leaf rolling by altering the number or size of bulliform cells. Overexpression of abaxially curled leaf 1 (ACL1) increases the number and exaggerates the size of bulliform cells, resulting in abaxially rolled leaves (Li et al, 2010). Overexpression of the zinc finger homeodomain (HD) class transcription factors OsZHD1 and OsZHD2 induced the abaxial leaf rolling due to the increased number of bulliform cells (Xu et al, 2014). The rice adaxialized leaf (adl1) mutant shows abaxially rolled leaves in which large bulliform-like cells are present on either side of leaf (Hibara et al, 2009). In the loss-of-function mutant of RL14 which encodes a 2OG-Fe oxygenase, altered composition of the secondary cell wall results in water deficiency and shrinkage of bulliform cells leading to incurved leaves (Fang et al, 2012)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
