Abstract
The development of above-ground lateral organs is initiated at the peripheral zone of the shoot apical meristem (SAM). The coordination of cell fate determination and the maintenance of stem cells are achieved through a complex regulatory network comprised of transcription factors. Two AP2/ERF transcription factor family genes, ESR1/DRN and ESR2/DRNL/SOB/BOL, regulate cotyledon and flower formation and de novo organogenesis in tissue culture. However, their roles in post-embryonic lateral organ development remain elusive. In this study, we analyzed the genetic interactions among SAM-related genes, WUS and STM, two ESR genes, and one of the HD-ZIP III members, REV, whose protein product interacts with ESR1 in planta. We found that esr1 mutations substantially enhanced the wus and stm phenotypes, which bear a striking resemblance to those of the wus rev and stm rev double mutants, respectively. Aberrant adaxial–abaxial polarity is observed in wus esr1 at relatively low penetrance. On the contrary, the esr2 mutation partially suppressed stm phenotypes in the later vegetative phase. Such complex genetic interactions appear to be attributed to the distinct expression pattern of two ESR genes because the ESR1 promoter-driving ESR2 is capable of rescuing phenotypes caused by the esr1 mutation. Our results pose the unique genetic relevance of ESR1 and the SAM-related gene interactions in the development of rosette leaves.
Highlights
When compared to the majority of animals taking a predetermined body plan, the development of terrestrial plants is more plastic and takes place post-embryonically by producing new organs throughout their lifespan
We employed the esr1-1/drn-2 and esr2-2 alleles because, unlike drn-1 drnl-2, esr1-1 esr2-2 double mutant plants still produce a small number of viable seeds, which enabled us to examine genetic interactions with wus or bum and to examine the corresponding triple mutant rosette leaf phenotypes
It is intriguing that the lateral organ phenotypes observed in the wus esr1 double mutant combinations bear a striking resemblance to those in wus-1 rev-6 [8], albeit the fact that single esr1 mutant alleles examined so far do not exhibit phenotypes found in rev single mutants
Summary
When compared to the majority of animals taking a predetermined body plan, the development of terrestrial plants is more plastic and takes place post-embryonically by producing new organs throughout their lifespan. Loss-of-function mutations in WUS resulted in the formation of an aberrant flat shoot apical meristem (SAM), the wus mutant retains an ability to develop vegetative leaves in a stop-and-go mode from either a defective SAM or ectopic meristem ( called lateral shoot meristem) that emerged from the axils of leaves and cotyledons, and eventually gives rise to the formation of inflorescence meristem [3] To account for this phenotype, the WUS-independent stem cell specification pathway is suggested [4]. In the later vegetative phase, esr partially rescued the retarded rosette leaf development observed in stm Such contradictory observations are reconciled by the fact that the expression of the ESR2 gene under the control of the regulatory sequences of ESR1 in wus esr rendered phenotypes indistinguishable from those in the wus single mutant, suggesting that the two ESR genes have redundant functions but their distinct expression patterns define their physiological relevance in the development of rosette leaves and the establishment of adaxial–abaxial polarity
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