Temporal regulation of shoot development inArabidopsis thalianabymiR156and its targetSPL3

Abstract

SPL3, SPL4 and SPL5 (SPL3/4/5) are closely related members of the SQUAMOSA PROMOTER BINDING PROTEIN-LIKE family of transcription factors in Arabidopsis, and have a target site for the microRNA miR156 in their 3Ј UTR. The phenotype of Arabidopsis plants constitutively expressing miR156-sensitive and miR156-insensitive forms of SPL3/4/5 revealed that all three genes promote vegetative phase change and flowering, and are strongly repressed by miR156. Constitutive expression of miR156a prolonged the expression of juvenile vegetative traits and delayed flowering. This phenotype was largely corrected by constitutive expression of a miR156-insensitive form of SPL3. The juvenile-to-adult transition is accompanied by a decrease in the level of miR156 and an increase in the abundance of SPL3 mRNA. The complementary effect of hasty on the miR156 and SPL3 transcripts, as well as the miR156-dependent temporal expression pattern of a 35S::GUS-SPL3 transgene, suggest that the decrease in miR156 is responsible for the increase in SPL3 expression during this transition. SPL3 mRNA is elevated by mutations in ZIPPY/AGO7, RNA DEPENDENT RNA POLYMERASE 6 (RDR6) and SUPPRESSOR OF GENE SILENCING 3 (SGS3), indicating that it is directly or indirectly regulated by RNAi. However, our results indicate that RNAi does not contribute to the temporal expression pattern of this gene. We conclude that vegetative phase change in Arabidopsis is regulated by an increase in the expression of SPL3 and probably also SPL4 and SPL5, and that this increase is a consequence of a decrease in the level of miR156.

The effects of carbon dioxide and temperature on microRNA expression in Arabidopsis development

“…The sequential action of Group I miRNAs, miR156/157 and miR172 control vegetative traits and the transitional timing from vegetative to reproductive phase during development 29 . Manipulations of the expression in these miRNAs can change Arabidopsis flowering time; for example, the overexpression of miR156 prolongs the juvenile phase and delays flowering time 29,34,41 , while its reduction is similar to SPLs overexpression, leading to the early-flowering phenotype 29,42 . Overexpressed miR172 also results in the early-flowering phenotype 29,43 .…”

Dual Effects of miR156-TargetedSPLGenes andCYP78A5/KLUHon Plastochron Length and Organ Size inArabidopsis thaliana

“…Although the phenotype was milder than that of the miR156 overexpressers, in which expression of eight additional SPL genes is strongly reduced (Schwab et al, 2005), this finding indicated an important redundant effect of SPL9 and SPL15 on plastochron length. Based on overexpression experiments, the SPL3 gene has been implicated primarily in the regulation of flowering time and phase change (Cardon et al, 1997;Wu and Poethig, 2006). Unfortunately, knockout alleles for the other two small SPL genes, SPL4 and SPL5, are not available, making it more difficult to test whether redundancy among the three small SPL genes masks their contribution to plastochron length.…”

Comparison of the genetic determinism of two key phenological traits, flowering and maturity dates, in three Prunus species: peach, apricot and sweet cherry

“…CUC2 protein is thought to act in the development of embryos and flowers (Aida et al, 1997). The second, SPL5, is part of the SPL family and has overlapping functions Genetic control of flowering and maturity dates in Prunus E Dirlewanger et al with SPL3 and SPL4 in the regulation of vegetative phase change in Arabidopsis (Wu and Poethig, 2006). The third one, SPA3, is a member of the SPA family that is essential for the inhibition of flowering under non-inductive short-day conditions (Laubinger and Hoecker, 2003).…”