thick tassel dwarf1encodes a putative maize ortholog of theArabidopsis CLAVATA1leucine-rich repeat receptor-like kinase

Abstract

Development in higher plants depends on the activity of meristems, formative regions that continuously initiate new organs at their flanks. Meristems must maintain a balance between stem cell renewal and organ initiation. In fasciated mutants, organ initiation fails to keep pace with meristem proliferation. The thick tassel dwarf1 (td1) mutation of maize affects both male and female inflorescence development. The female inflorescence, which results in the ear, is fasciated, with extra rows of kernels. The male inflorescence, or tassel, shows an increase in spikelet density. Floral meristems are also affected in td1 mutants; for example, male florets have an increase in stamen number. These results suggest that td1 functions in the inflorescence to limit meristem size. In addition, td1 mutants are slightly shorter than normal siblings, indicating that td1 also plays a role in vegetative development. td1 encodes a leucine-rich repeat receptorlike kinase (LRR-RLK) that is a putative ortholog of the Arabidopsis CLAVATA1 protein. These results complement previous work showing that fasciated ear2 encodes a CLAVATA2-like protein, and suggest that the CLAVATA signaling pathway is conserved in monocots. td1 maps in the vicinity of quantitative trait loci that affect seed row number, spikelet density and plant height. We discuss the possible selection pressures on td1 during maize domestication.Key words: Meristem, Stem cells, Inflorescence, thick tassel dwarf1, Maize Summary thick tassel dwarf1 encodes a putative maize ortholog of the Arabidopsis

CLAVATA-WUSCHEL signaling in the shoot meristem

“…td1 and fea2 mutants show striking enlargement/fasciation of inflorescence meristems and an increase in spikelet density with occasional abnormal floral phenotypes, indicating that TD1 and FEA2 are negative regulators of the SAM, as in Arabidopsis (Bommert et al, 2005;TaguchiShiobara et al, 2001). TD1 transcripts are detected in the peripheral region of the maize vegetative SAM and in leaf primordia, but not in the CZ.…”

“…TD1 transcripts are detected in the peripheral region of the maize vegetative SAM and in leaf primordia, but not in the CZ. In inflorescences, however, TD1 is expressed throughout the outer cell layers of the inflorescence meristem and on its flanks at positions of spikelet pair meristem (SPM) initiation (Bommert et al, 2005). The implications of these changing expression patterns are unclear, since TD1 functions more specifically in the inflorescence meristem, and its vegetative function is not clear.…”

Quantitative trait loci mapping for kernel row number using chromosome segment substitution lines in maize

“…Upadyayula et al (2006) identified a set of QTL for tassel branch number, central spike spikelet pair density, kernel number density, kernel row number, kernel number per row, and cob diameter. Some of these parameters were co-located with genes that are known to affect the development of maize inflorescences, such as ramosa1 , ramosa2, thick tassel dwarf1 (Bommert et al, 2005), and fasciated ear2 (Taguchi-Shiobara et al, 2001); however, other genes in the QTL regions were unknown. We found that only a few cloned mutant genes were closely linked with the QTL detected for KRN in this investigation.…”

Expression Level ofABERRANT PANICLE ORGANIZATION1Determines Rice Inflorescence Form through Control of Cell Proliferation in the Meristem

“…Rice floral organ number1 ( fon1), fon2, and maize fascinated ear and thick tassel dwarf1, all defective in the CLAVATA signaling pathway, contain enlarged SAMs and exhibit abnormal branching patterns (Taguchi-Shiobara et al, 2001;Suzaki et al, 2004Suzaki et al, , 2006Bommert et al, 2005b;Chu et al, 2006). In contrast, the lonely guy (log) mutant that has a defect in synthesis of active cytokinins (CKs) has a small SAM and produces an inflorescence markedly reduced in size (Kurakawa et al, 2007).…”