Leaf Rolling Controlled by the Homeodomain Leucine Zipper Class IV GeneRoc5in Rice  

Abstract

Leaf rolling is considered an important agronomic trait in rice (Oryza sativa) breeding. To understand the molecular mechanism controlling leaf rolling, we screened a rice T-DNA insertion population and isolated the outcurved leaf1 (oul1) mutant showing abaxial leaf rolling. The phenotypes were caused by knockout of Rice outermost cell-specific gene5 (Roc5), an ortholog of the Arabidopsis (Arabidopsis thaliana) homeodomain leucine zipper class IV gene GLABRA2. Interestingly, overexpression of Roc5 led to adaxially rolled leaves, whereas cosuppression of Roc5 resulted in abaxial leaf rolling. Bulliform cell number and size increased in oul1 and Roc5 cosuppression plants but were reduced in Roc5-overexpressing lines. The data indicate that Roc5 negatively regulates bulliform cell fate and development. Gene expression profiling, quantitative polymerase chain reaction, and RNA interference (RNAi) analyses revealed that Protodermal Factor Like (PFL) was probably down-regulated in oul1. The mRNA level of PFL was increased in Roc5-overexpressing lines, and PFL-RNAi transgenic plants exhibit reversely rolling leaves by reason of increases of bulliform cell number and size, indicating that Roc5 may have a conserved function. These are, to our knowledge, the first functional data for a gene encoding a homeodomain leucine zipper class IV transcriptional factor in rice that modulates leaf rolling.

SEMI-ROLLED LEAF1 Encodes a Putative Glycosylphosphatidylinositol-Anchored Protein and Modulates Rice Leaf Rolling by Regulating the Formation of Bulliform Cells

“…Ectopic expression of micro-RNA166-resistant version of the OsHB1 gene, a member of class III homeodomain Leu zipper family, results in adaxially rolled leaves with reduced sclerenchyma and formation of bulliform cells at the abaxial side (Itoh et al, 2008). Loss-of-function mutant of OUTCURVED LEAF1 (OUL1)/Rice outermost cell-specific gene5 (Roc5), an ortholog of Arabidopsis (Arabidopsis thaliana) homeodomain Leu zipper class IV gene GLABRA2, presents the increased number and size of bulliform cells, resulting in abaxially rolled leaves, whereas overexpression of OUL1/Roc5 results in reduced number and size of bulliform cells, leading to adaxial leaf rolling (Ito et al, 2003;Zou et al, 2011). The leaves of rice transgenic plants with cosuppression of YABBY1 were also abaxially rolled due to the increased number of bulliform cells at the adaxial side (Dai et al, 2007).…”

Investigation of triterpene synthesis and regulation in oats reveals a role for β-amyrin in determining root epidermal cell patterning

“…These sequences together form a monocot-specific subclade within the α-clade of the plant HD-ZIP IV superfamily (29). OCL1 and ROC5 are expressed in the epidermal cell layers of organs in monocots and are involved in regulation of processes such as the determination of epidermal cell fate, anthocyanin accumulation, and root development (30,31). The wider α-clade includes the A. thaliana HD-ZIP IV proteins HDG1, HDG6, HDG7, and ANL2 (24,32).…”

Description of the Family, Vegetative Morphology and Anatomy

“…Transcription factors that help specify identity of the ad-and abaxial sides of the leaf blade determine whether bulliforms will develop on the adaxial side (as is most common) or abaxial side, and also regulate how many bulliforms form in a cluster (Dai et al 2007;Zhang et al 2009;Zou et al 2011). Various enzymes also affect bulliform cell development (Fujino et al 2008;Hu et al 2010;Li et al 2010;Xiang et al 2012), in some cases via affecting the differentiation between the ab-and adaxial sides of the leaf (Hibara et al 2009).…”