Disease relevance of AS1

• We also report the effects on leaf polarity of overexpression of the AS1 or AS2 genes under the control of the cauliflower mosaic virus (CAMV) 35S promoter [1].
• ERECTA is required for protection against heat-stress in the AS1/ AS2 pathway to regulate adaxial-abaxial leaf polarity in Arabidopsis [2].

High impact information on AS1

• AS1 encodes a myb domain protein, closely related to PHANTASTICA in Antirrhinum and ROUGH SHEATH2 in maize, both of which negatively regulate knotted-class homeobox genes [3].
• GTE6 positively regulates the expression of ASYMMETRIC LEAVES1 (AS1), which encodes a myb-domain protein that controls proximodistal patterning of leaves [4].
• Chromatin remodeling at AS1 is a key regulatory mechanism in leaf development, which ensures the continual production of mature leaves following juvenile-adult transition, thereby maintaining the identity of the mature vegetative phase [4].
• Using chromatin immunoprecipitation (ChIP) assays, we show that GTE6 is associated with the promoter and the start of the transcribed region of AS1 and up-regulates expression of AS1 through acetylation of histones H3 and H4 [4].
• We have analyzed the development of leaf shape and vascular pattern in leaves mutant for ASYMMETRIC LEAVES1 (AS1) or AS2 and compared the timing of developmental landmarks to cellular response to auxin, as measured by expression of the DR5:beta-glucuronidase (GUS) transgene and to cell division, as measured by expression of the cycB1:GUS transgene [5].

Biological context of AS1

• The Myb domain gene PHANTASTICA (PHAN) is required for adaxial fate in many plants , but the Arabidopsis ortholog ASYMMETRIC LEAVES1 (AS1) has milder effects, suggesting that alternate or redundant pathways exist . We describe enhancers of as1 with more elongate and dissected leaves [6].
• The promoters for the AS1 and AS2 genes of pea were isolated, sequenced, and functionally dissected for their ability to confer regulated expression to the GUS reporter gene in transgenic tobacco [7].
• AS1 is expressed nearly ubiquitously, consistent with the pleiotropic mutant phenotypes [8].
• The mutant phenotypes suggest that the ASYMMETRIC LEAVES1 ( AS1) gene is involved in the control of cell differentiation in leaves [8].

Associations of AS1 with chemical compounds

• We propose that regulatory interactions between auxin, AS1 and KNOX activities may both direct leaf initiation and sculpt leaf form [9].

Regulatory relationships of AS1

• Here, we show that auxin and AS1 pathways converge to repress expression of the KNOX gene BREVIPEDICELLUS (BP) and thus promote leaf fate [9].
• These findings suggest that, in leaves, the AS2 and AS1 genes repress the expression of these homeobox genes, which are thought to maintain the indeterminate cell state in the shoot apical meristem [10].

Other interactions of AS1

• Genetic interactions with a second gene, ASYMMETRIC LEAVES2 (AS2), indicate it acts at the same position in this hierarchy as AS1 [11].
• In addition, the RNA-DEPENDENT RNA POLYMERASE6 (RDR6) gene acts synergistically with AS1 and AS2 to specify the adaxial polarity and repress the KNOX genes in leaves [12].
• The Arabidopsis thaliana ASYMMETRIC LEAVES1 (AS1) and AS2 genes are important for repressing class I KNOTTED1-like homeobox (KNOX) genes and specifying leaf adaxial identity in leaf development [13].
• A possible model of the AS1, AS2 and ER action in leaf polarity formation is discussed [1].

References