Abstract
The phytohormone auxin (indole-3-acetic acid [IAA]) plays a fundamental role in vegetative and reproductive plant
development. Here, we characterized a seed-specific viable maize (Zea mays) mutant, defective endosperm18 (de18) that is
impaired in IAA biosynthesis. de18 endosperm showed large reductions of free IAA levels and is known to have
approximately 40% less dry mass, compared with De18. Cellular analyses showed lower total cell number, smaller cell
volume, and reduced level of endoreduplication in the mutant endosperm. Gene expression analyses of seed-specific
tryptophan-dependent IAA pathway genes, maize Yucca1 (ZmYuc1), and two tryptophan-aminotransferase co-orthologs were
performed to understand the molecular basis of the IAA deficiency in the mutant. Temporally, all three genes showed high
expression coincident with high IAA levels; however, only ZmYuc1 correlated with the reduced IAA levels in the mutant
throughout endosperm development. Furthermore, sequence analyses of ZmYuc1 complementary DNA and genomic clones
revealed many changes specific to the mutant, including a 2-bp insertion that generated a premature stop codon and a truncated
YUC1 protein of 212 amino acids, compared with the 400 amino acids in the De18. The putative, approximately 1.5-kb, Yuc1
promoter region also showed many rearrangements, including a 151-bp deletion in the mutant. Our concurrent high-density
mapping and annotation studies of chromosome 10, contig 395, showed that the De18 locus was tightly linked to the gene
ZmYuc1. Collectively, the data suggest that the molecular changes in the ZmYuc1 gene encoding the YUC1 protein are the causal
basis of impairment in a critical step in IAA biosynthesis, essential for normal endosperm development in maize.
Lingua originale | English |
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pagine (da-a) | 1318-1328 |
Numero di pagine | 11 |
Rivista | Plant Physiology |
Stato di pubblicazione | Pubblicato - 2012 |
Keywords
- Defective endosperm 18
- Zea mays
- auxin
- endoreduplication