Plant Gene Expression Center

Identification of a new dominant leaf mutant from B73 EMS mutagenesis

— Gerhold, A; Candela-Anton, H; Neuffer, G; Hake, S

We identified a new dominant mutant in our F1 population derived from EMS mutagenesis of B73 pollen crossed onto B73 ears. The F1 plant was a half-plant chimera, showing the defect in only one vertical half of the plant. The mutation transmitted to the next generation and was observed in a population of 20. It is fully expressive and penetrant in the A632/B73 background. We have tentatively named the mutant Liguleless narrow* (Lgn*).

Normal maize leaves are composed of a blade, which lies flat, and a sheath, which hugs the culm. At the junction of the blade and sheath are the auricle and ligule (Figure 1, right). Lgn* leaves are narrower and have a disrupted sheath/blade boundary from leaf 5 to leaf 15. At its most severe, approximately at leaf 10, the leaf is very narrow, the ligule appears only as a patch at the midrib, and the sheath extends up into the blade at the margin (Figure 1, left). The leaf is narrow at both the midpoint of the blade and at the blade/sheath junction. This phenotype is reminiscent of the double mutant between Wavy auricle in blade1 (Wab1) and liguleless1 (lg1) (Foster et al. 2004, Development 131:392). We also see extension of the blade into the sheath at the margin, which was not seen in Wab1; lg1 doubles. The disruption of blade/sheath patterning occurs on both sides of the midrib, but is not always symmetrical, similar to liguleless2 mutants (Harper and Freeling 1996, Genetics 144:1871). The phenotype recovers gradually; older leaves have an entire ligule with a somewhat uneven auricle/blade boundary, and, eventually, all leaves are normal in the proximal distal patterning, but still are narrower (Figure 1). Lgn* mutants have a shorter blade, but the sheaths are the same length as those of their normal siblings.


Figure 1: From left to right — Lgn* leaf 11, Lgn* leaf 12, Lgn* leaf 15 and wild-type sibling leaf 11. Note the reduced ligule in leaves 11 and 12, and the recovery of ligule in leaf 15. Lgn* leaf 11 shows sheath extensions into blade, while leaf 12 shows blade extensions below the ligule-auricle boundary.


We also noticed an obvious tassel phenotype in the mutants. Branch number is severely reduced and the branch angle appears more acute. lg2 mutants also have a tassel phenotype, lacking tassel branches altogether (Walsh and Freeling 1999, Plant J. 19:489).

We are in the process of mapping the mutation by bulked segregant analysis and crossing Lgn* to other leaf mutants.


Figure 2: Lgn* tassel (left) as compared with a wild-type sibling (right). The number of branches is noticeably reduced and the branch angle is more upright.

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