Genetic and molecular analysis of trichome development in Arabis alpina

Abstract

The genetic and molecular analysis of trichome development in Arabidopsis thaliana has generated a detailed knowledge about the underlying regulatory genes and networks. However, how rapidly these mechanisms diverge during evolution is unknown. To address this problem, we used an unbiased forward genetic approach to identify most genes involved in trichome development in the related crucifer species Arabis alpina. In general, we found most trichome mutant classes known in A. thaliana. We identified orthologous genes of the relevant A. thaliana genes by sequence similarity and synteny and sequenced candidate genes in the A. alpina mutants. While in most cases we found a highly similar genephenotype relationship as known from Arabidopsis, there were also striking differences in the regulation of trichome patterning, differentiation, and morphogenesis. Our analysis of trichome patterning suggests that the formation of two classes of trichomes is regulated differentially by the homeodomain transcription factor AaGL2. Moreover, we show that overexpression of the GL3 basic helix-loop-helix transcription factor in A. alpina leads to the opposite phenotype as described in A. thaliana. Mathematical modeling helps to explain how this nonintuitive behavior can be explained by different ratios of GL3 and GL1 in the two species.Arabis alpina | trichomes | genetic analysis

Evolutionary Comparison of the Developmental/Physiological Phenotype and the Molecular Behavior of SPIRRIG Between Arabidopsis thaliana and Arabis alpina

“…In our phylogenetic analysis, we found the SPI gene well conserved in all plant species analyzed ( Supplementary Figure S1 ). In Arabis alpina , the orthologous SPI gene was identified by sequence homology and the synteny of homologous genes on the chromosome ( Chopra et al, 2019 ). Three spi mutants were identified in an EMS mutagenesis screen for trichome phenotypes ( Chopra et al, 2019 ) in the perpetual flowering 1 ( pep1 ) mutant, in the pajares (paj) ecotype background ( Wang et al, 2009 ).…”

“…In Arabis alpina , the orthologous SPI gene was identified by sequence homology and the synteny of homologous genes on the chromosome ( Chopra et al, 2019 ). Three spi mutants were identified in an EMS mutagenesis screen for trichome phenotypes ( Chopra et al, 2019 ) in the perpetual flowering 1 ( pep1 ) mutant, in the pajares (paj) ecotype background ( Wang et al, 2009 ). This line harbors a mutation in the floral repressor PEP1 , which causes the plants to flower without vernalization ( Albani et al, 2012 ).…”

“…The three Aaspi alleles had been identified by their weak distorted trichome phenotype ( Chopra et al, 2019 ; Figure 2 ). In Arabidopsis, it was shown that spi mutant trichomes exhibit a reduced stalk length and width and a reduced average branch length ( Saedler et al, 2009 ).…”

“…Would the molecular behavior be comparable? Using three Aaspi mutants identified in an exhaustive EMS screen for trichome mutants in A. alpina ( Chopra et al, 2019 ) we reveal a similar molecular behavior and phenotypes, though the phenotypes show distinct differences.…”

Genetic determinism of prickles in rose

“…Until recently, only a few studies had been published about the molecular regulation of prickle development, but great progress has been made in trichome initiation and development, especially in Arabidopsis. Several transcription factors (TFs) such as MYB, bHLH, WD40, WRKY and C2H2 zinc finger families' proteins have been identified as being involved in trichome initiation and development (reviewed in Balkunde et al (2010), Pattanaik et al (2014), Ma et al (2016a), Huchelmann et al (2017) and Chopra et al (2019)). A trimeric activator complex consisting of MYB (GLABRA1) -bHLH (GLABROUS3/ENHANCER OF GL3) -WDR (TRANSPARENT TESTA GL1) plays a key role in trichome development (Zhang 2003;Kirik et al 2005;Patra et al 2013).…”