Identification of the Teopod1, Teopod2, and Early Phase Change genes in maize

Abstract

Teopod1(Tp1), Teopod2(Tp2), and Early Phase Change (Epc) have profound effects on the timing of vegetative phase change in maize. Gain-of-function mutations in Tp1 and Tp2 delay all known phase-specific vegetative traits, whereas loss-of-function mutations in Epc accelerate vegetative phase and cause shoot abortion in some genetic backgrounds. Here we show that that Tp1 and Tp2 likely represent cis-acting mutations that cause the over-expression of, respectively, Zma-miR156j and Zma-miR156h. Epc is the maize orthologue of HASTY, an Arabidopsis gene that stabilizes miRNAs and promotes their intracellular movement. Consistent with its pleotropic phenotype and epistatic interaction with Tp1 and Tp2, epc reduces the level of miR156 and several other miRNAs.

Temporal regulation of vegetative phase change in plants

“…Loss-of-function mutations in tsh4 cause the development of bracts in the inflorescence 144 , while plants triply mutant for tsh4, ub2 and ub3 have numerous tillers, an unbranched leafy inflorescence, and flower at the same time as wild type but produce more leaves than normal because they have an elevated rate of leaf initiation 145 . This phenotype is very similar to that of Corngrass, Teopod1, and Teopod2 30,146,147 , all of which cause the overexpression of miR156 67,69,70 , but whether tsh4, ub2 and ub3 regulate leaf traits associated with vegetative phase change is unknown because these traits were not examined in these studies. The rice gene, OsSPL14-also known as Wealthy Farmer's Panicle (WFP) 148 , and Ideal Plant Architecture (IPA) 149 -is closely related to tsh4, ub2 and ub3, and has a similar function.…”

“…This result revealed that maize possesses juvenile and adult vegetative phases, and that the transition between these phases is under genetic control. It opened the way to subsequent genetic analyses of vegetative phase change in both maize 32,[54][55][56][57][58][59][60][61] and Arabidopsis 37,[62][63][64] and to the discovery that the microRNA miR156 is the master regulator of this transition [65][66][67][68][69][70] .…”

“…Consequently, leaf number-which is commonly used as a proxy for flowering time-is a poor predictor of flowering time in plants with elevated or reduced levels of miR156 or SPL proteins. The Tp2 mutant of maize, for example, has an elevated level of miR156 due to the over-expression of Zma-miR156h 69,70 . This mutant has an increased number of leaves and a small unbranched tassel with only a few flowers, but does not exhibit a major delay in its sensitivity to a floral inductive photoperiodic stimulus, and terminates shoot development at same time as wild type plants 56 ; the "leafy" phenotype of this mutant is attributable to a delay in the floral meristem identity transition, not to a delay in the acquisition of reproductive competence.…”