Provided are methods for generating modified plants, seedlings or seeds, comprising introducing into, or engineering in a plant cell, a nucleic acid encoding a mutant AHL protein having a mutation of the AT hook domain that confers a dominant negative phenotype as disclosed herein. Nucleic acids encoding a polypeptide comprising SEQ ID NO:3, SEQ ID NO:6, a polypeptide having at least 93% or at least 95% sequence identity with SEQ ID NO:3, or a polypeptide having at least 75% or at least 80% sequence identity with SEQ ID NO:6 are provided, along with such polypeptides having a mutation of the AT hook domain that confers a dominant negative phenotype as disclosed herein. In particular aspects, the polypeptide lacks the AT hook domain thereof. In certain aspects, the polypeptide comprises an intact or functional PPC domain, and preferably additionally comprises the linker region between the PPC domain and the AT-hook domain.
STATEMENT REGARDING FEDERALLY-SPONSORED RESEARCH
 This invention was made with government support under Contract No. DE-FG02-08ER15927 awarded by the Department of Energy (DOE). The Government has certain rights in the invention.