Suppression of An Auxin F-Box Like Gene Is Linked to the ‘Greens-Type' Phenotype in Poa Annua L.

The greens-type phenotype in Poa annua L. links single branched inflorescences with dwarfed culms, tillers, panicles, leaves and number of spikelets to a single mechanism. In general, this phenotype is a reduction in plant stature as compared to the annual-type. In Arabidopsis, Auxin F-Box proteins are required for proper auxin signaling. The triple and quadruple Auxin F-Box mutants are auxin resistant and display a dwarf phenotype. Auxin signaling mutants also cross-talk with the gibberellic acid pathway by up-regulating the late GA-biosynthetic genes. In the present study, GA3 and 1-naphthaleneacetic acid (NAA) were used in plant hormone bioassays while auxin signaling and GA biosynthetic genes were PCR cloned and used for expression analysis on annual-type and greens-type P. annua. The results indicate that the greens-type biotype is responsive to GA3 , resistant to NAA, and GA20 oxidase is up-regulated in comparison to the annual-type. Moreover, a 518 bp length fragment was cloned from P. annua and shows high sequence homology to Auxin F-Box sequences from rice, maize, and Arabidopsis. RT-PCR and Real-Time analysis suggest that the greens-type phenotype is correlated to a reduction in the expression of this Auxin F-Box like gene. In addition, preliminary results from microRNA, DNA methylation, and mowing experiments will be discussed in the context of the Auxin F-box ’s regulation and our previous results which documented the greens-type’s instability.