Maize DELLA Proteins dwarf plant8 and dwarf plant9 as Modulators of Plant Development

Abstract

DELLA proteins are nuclear-localized negative regulators of gibberellin signaling found ubiquitously throughout higher plants. Dominant dwarfing mutations of DELLA proteins have been primarily responsible for the dramatic increases in harvest index of the 'green revolution'. Maize contains two genetic loci encoding DELLA proteins, dwarf plant8 (d8) and dwarf plant 9 (d9). The d8 gene and three of its dominant dwarfing alleles have been previously characterized at the molecular level. Almost 20 years after the initial description of the mutant, this investigation represents the first molecular characterization of d9 and its gibberellin-insensitive mutant, D9-1. We have molecularly, subcellularly and phenotypically characterized the gene products of five maize DELLA alleles in transgenic Arabidopsis. In dissecting the molecular differences in D9-1, a critical residue for normal DELLA function has been uncovered, corresponding to E600 of the D9 protein. The gibberellin-insensitive D9-1 was found to produce dwarfing and, notably, earlier flowering in Arabidopsis. Conversely, overexpression of the D9-1 allele delayed flowering in transgenic maize, while overexpression of the d9 allele led to earlier flowering. These results corroborate findings that DELLA proteins are at the crux of many plant developmental pathways and suggest differing mechanisms of flowering time control by DELLAs in maize and Arabidopsis.

The Maize MID-COMPLEMENTING ACTIVITY Homolog CELL NUMBER REGULATOR13/NARROW ODD DWARF Coordinates Organ Growth and Tissue Patterning

“…To test if GA deficiency is causal to the nod-1 phenotypes, we applied exogenous GA 3 to 2-week-old plants. The treatment rescued the GA biosynthesis-deficient mutant d1 (Chen et al, 2014) but not the GA insensitive D9 mutant (Lawit et al, 2010). In nod-1, GA 3 application caused a small increase in stem height, but failed to rescue the other pleiotropic phenotypes (Supplemental Figures 7E and 7F).…”

MOLECULAR BASIS OF THE DWARFISM CHARACTER IN CULTIVATED PLANTS. II. DELLA-PROTEINS: STRUCTURE AND FUNCTIONS (review)

“…Maize [2,9,10] d8(+) D8 Increased D8 stability in the presence of GA (Val 103 insertion into the TVHYNP domain)…”

“…GA-insensitive dwarf plants Maize [9,10] rht-1 Rht (Reduced height) GA-insensitive; failure to form GA-GID1-Rht complex, Rht stability (DELLA lesion caused by a deletion) …”

“…These induce 26S proteasome-dependent degradation of DELLA proteins. Changes in DELLA structure which resulted in dwarfism were reported in D8 (Dwarf plant 8) and D9 maize mutants [2,9,10], Rht (Reduced height) wheat mutant [2,11], DWF2 (Dwarf 2) turnip mutant [12] and VvGAI (Vitis vinifera GAI) grape mutant [13] (Table).…”

“…DELLA family proteins are nuclear-localized [10,25,26] and containing nuclear localization signal [10,20]. DELLA means a characteristic conserved sequence of Asp-Glu-Leu-Leu-Ala ((D-E-L-L-A) at the N-end of the polypeptide.…”