The barren stalk2 Gene Is Required for Axillary Meristem Development in Maize

Abstract

The diversity of plant architecture is determined by axillary meristems (AMs). AMs are produced from small groups of stem cells in the axils of leaf primordia and generate vegetative branches and reproductive inflorescences. Previous studies identified genes critical for AM development that function in auxin biosynthesis, transport, and signaling. barren stalk1 (ba1), a basic helix-loop-helix transcription factor, acts downstream of auxin to control AM formation. Here, we report the cloning and characterization of barren stalk2 (ba2), a mutant that fails to produce ears and has fewer branches and spikelets in the tassel, indicating that ba2 functions in reproductive AM development. Furthermore, the ba2 mutation suppresses tiller growth in the teosinte branched1 mutant, indicating that ba2 also plays an essential role in vegetative AM development. The ba2 gene encodes a protein that co-localizes and heterodimerizes with BA1 in the nucleus. Characterization of the genetic interaction between ba2 and ba1 demonstrates that ba1 shows a gene dosage effect in ba2 mutants, providing further evidence that BA1 and BA2 act together in the same pathway. Characterization of the molecular and genetic interaction between ba2 and additional genes required for the regulation of ba1 further supports this finding. The ba1 and ba2 genes are orthologs of rice genes, LAX PANICLE1 (LAX1) and LAX2, respectively, hence providing insights into pathways controlling AMs development in grasses.

The Ha‐ROXL gene is required for initiation of axillary and floral meristems in sunflower

“…The different severity of FM defects in mutants of Arabidopsis , maize or sunflower could be related to the distinctive inflorescence architecture of these three species (Hernández & Green, 1993;McSteen & Hake, 2001; Wang et al, . ; Yang et al, 2012; Yao et al, ). The raceme of Arabidopsis is an indeterminate inflorescence, where apical meristem grows indefinitely, generating a continuous main axis that laterally produces FMs after a single branching step (Long & Barton, ).…”

“…In rice, LAX1 physically interacts with LAX2 a plant‐specific nuclear factor (Tabuchi et al, ). Different genes regulate ZmBA1 that is also transcriptionally regulated by auxin (reviewed by McSteen, 2010); recently, Yao et al () demonstrated that the BA2 contains a protein–protein interaction domain and physically interacts with BA1. The maize gene BA2 is the ortholog of the rice LAX2 gene but notably, the closest orthologs of BA2 / LAX2 in the dicot Arabidopsis have not yet been functionally characterized (Yao et al, ).…”

“…Different genes regulate ZmBA1 that is also transcriptionally regulated by auxin (reviewed by McSteen, 2010); recently, Yao et al () demonstrated that the BA2 contains a protein–protein interaction domain and physically interacts with BA1. The maize gene BA2 is the ortholog of the rice LAX2 gene but notably, the closest orthologs of BA2 / LAX2 in the dicot Arabidopsis have not yet been functionally characterized (Yao et al, ). Furthermore, how the interaction of BA2 with BA1 affects the expression of downstream target genes is currently unknown (Yao et al, ).…”

“…The maize gene BA2 is the ortholog of the rice LAX2 gene but notably, the closest orthologs of BA2 / LAX2 in the dicot Arabidopsis have not yet been functionally characterized (Yao et al, ). Furthermore, how the interaction of BA2 with BA1 affects the expression of downstream target genes is currently unknown (Yao et al, ). Ha‐ROXL might dimerize with another a bHLH TF, as it happens in rice for LAX and SMALL PANICLE (SPA; Komatsu et al, ).…”

Plant Inflorescence Architecture: The Formation, Activity, and Fate of Axillary Meristems

“…The BA1 homolog in rice, LAX PANICLE 1 (LAX1) also promotes initiation of lateral organs (Komatsu et al 2003). In maize and rice, similar BA1/LAX1 interacting nuclear proteins with putative RAWUL/PDZ/ SH3 domains called BA2 (Yao et al 2019) or LAX2 (Tabuchi et al 2011) were identified. LAX2 links to auxin response in other processes by blocking the interaction between Aux/IAA proteins and ARFs (Li et al 2018).…”