Abstract
The maize shoot apical meristem (SAM) comprises a small pool of stem cells that generate all above-ground organs. Although mutational studies have identified genetic networks regulating SAM function, little is known about SAM morphological variation in natural populations. Here we report the use of high-throughput image processing to capture rich SAM size variation within a diverse maize inbred panel. We demonstrate correlations between seedling SAM size and agronomically important adult traits such as flowering time, stem size and leaf node number. Combining SAM phenotypes with 1.2 million single nucleotide polymorphisms (SNPs) via genome-wide association study reveals unexpected SAM morphology candidate genes. Analyses of candidate genes implicated in hormone transport, cell division and cell size confirm correlations between SAM morphology and trait-associated SNP alleles. Our data illustrate that the microscopic seedling SAM is predictive of adult phenotypes and that SAM morphometric variation is associated with genes not previously predicted to regulate SAM size.
Highlights
The maize shoot apical meristem (SAM) comprises a small pool of stem cells that generate all above-ground organs
Single-gene mutations within these SAM genetic networks can alter the morphology of both the shoot meristem and the plant[9,10], revealing that SAM structure and function are intimately linked. These studies identified a number of genes required for SAM function, little is known about the genetic control of SAM morphological variation in large natural populations or in diverse breeding stocks
Utilizing a 1.2 million single nucleotide polymorphism (SNP) data set that combined RNAseq-generated and previously published available genotypes, we identify candidate genes associated with SAM morphological variation
Summary
The maize shoot apical meristem (SAM) comprises a small pool of stem cells that generate all above-ground organs. Single-gene mutations within these SAM genetic networks can alter the morphology of both the shoot meristem and the plant[9,10], revealing that SAM structure and function are intimately linked. These studies identified a number of genes required for SAM function, little is known about the genetic control of SAM morphological variation in large natural populations or in diverse breeding stocks. Significant correlations are identified between the microscopic SAM and several adult phenotypes, including flowering time, stem width and leaf node number These findings demonstrate that the morphology of the seedling SAM is predictive of agronomically important adult plant traits. The majority of these GWAS-derived SAM candidate genes have not been previously implicated in studies of SAM structure, subsequent analyses of candidate genes with putative functions in hormone transport, cell division and cell expansion support their predicted contributions to maize SAM morphological diversity
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