The maize fused leaves1 (fdl1) gene controls organ separation in the embryo and seedling shoot and promotes coleoptile opening

The fdl1-1 mutation, caused by an Enhancer/Suppressor mutator (En/Spm) element insertion located in the third exon of the gene, identifies a novel gene encoding ZmMYB94, a transcription factor of the R2R3-MYB subfamily. The fdl1 gene was isolated through co-segregation analysis, whereas proof of gene identity was obtained using an RNAi strategy that conferred less severe, but clearly recognizable specific mutant traits on seedlings. Fdl1 is involved in the regulation of cuticle deposition in young seedlings as well as in the establishment of a regular pattern of epicuticular wax deposition on the epidermis of young leaves. Lack of Fdl1 action also correlates with developmental defects, such as delayed germination and seedling growth, abnormal coleoptile opening and presence of curly leaves showing areas of fusion between the coleoptile and the first leaf or between the first and the second leaf. The expression profile of ZmMYB94 mRNA\u2014determined by quantitative RT-PCR\u2014 overlaps the pattern of mutant phenotypic expression and is confined to a narrow developmental window. High expression was observed in the embryo, in the seedling coleoptile and in the first two leaves, whereas RNA level, as well as phenotypic defects, decreases at the third leaf stage. Interestingly several of the Arabidopsis MYB genes most closely related to ZmMYB94 are also involved in the activation of cuticular wax biosynthesis, suggesting deep conservation of regulatory processes related to cuticular wax deposition between monocots and dicots

Interaction between different genes controlling endosperm development in maize

In this report we present the results of a complementation test involving nine emp (empty pericarp) mutants of maize that represent single gene mutants, isolated as independent events. These mutants are embryo lethal at maturity and drastically reduced in their endosperm size. They can be subdivided in two major subgroups: those with a flat appearance of the kernel and those with a wrinkled pericarp. By crossing inter-se plants heterozygous for emp mutants, we identified those non-complementing (that means allelic) and those complementing (that means not allelic) in the F1 generation. Most results in the F1 were concordant to those obtained in the F2 generation with the exception of four cases where the F1 results suggest allelism (i.e. one gene) whereas those in the F2 segregation of two genes. This intriguing result seems to suggest an interaction between different emp mutants due to second site non-complementation (SSNC). In addition while scoring ears segregating for a single emp mutant, in different genetic backgrounds, we noticed that some mutant seeds exhibited a more abundant endosperm tissue and occasionally an embryonic axis. About 10% of these seeds germinate yielding slow growing seedlings. This observation could be explained by assuming that emp mutants introduced in different genetic backgrounds uncover a cryptic variability. This point needs to be further investigated but if confirmed, emp mutants could be used as a tool for the detection of genetic factors contributing to the amount of endosperm in the maize kernel to exploit in breeding programs

BASIC PENTACYSTEINE1, a GA Binding Protein That Induces Conformational Changes in the Regulatory Region of the Homeotic Arabidopsis Gene SEEDSTICK

The mechanisms for the regulation of homeotic genes are poorly understood in most organisms, including plants. We identified BASIC PENTACYSTEINE1 (BPC1) as a regulator of the homeotic Arabidopsis thaliana gene SEEDSTICK (STK), which controls ovule identity, and characterized its mechanism of action. A combination of tethered particle motion analysis and electromobility shift assays revealed that BPC1 is able to induce conformational changes by cooperative binding to purine-rich elements present in the STK regulatory sequence. Analysis of STK expression in the bpc1 mutant showed that STK is upregulated. Our results give insight into the regulation of gene expression in plants and provide the basis for further studies to understand the mechanisms that control ovule identity in Arabidopsis