ABSTRACT
Water availability is a significant constraint to crop production, and increasing drought tolerance of crops is one step to gaining greater yield stability. Excellent progress has been made using models to identify pathways and genes that can be manipulated through biotechnology to improve drought tolerance. A current focus is on translation of results from models in controlled environments to crops in the field. Field testing to demonstrate improved yields under water-limiting conditions is challenging and expensive. More extensive phenotyping of transgenic lines in the greenhouse may contribute to improved predictions about field performance. It is possible that multiple mechanisms of drought tolerance may be needed to provide benefit across the diversity of water stress environments relevant to economic yield.
Subject(s)
Agriculture/methods , Biotechnology/methods , Plants, Genetically Modified/physiology , Water , Droughts , Plant Physiological Phenomena , Plants, Genetically Modified/growth & developmentABSTRACT
BROTHER OF LUX ARRHYTHMO (BOA) is a GARP family transcription factor in Arabidopsis thaliana and is regulated by circadian rhythms. Transgenic lines that constitutively overexpress BOA exhibit physiological and developmental changes, including delayed flowering time and increased vegetative growth under standard growing conditions. Arabidopsis circadian clock protein CIRCADIAN CLOCK ASSOCIATED1 (CCA1) binds to the evening element of the BOA promoter and negatively regulates its expression. Furthermore, the period of BOA rhythm was shortened in cca1-11, lhy-21 (for LATE ELONGATED HYPOCOTYL), and cca1-11 lhy-21 genetic backgrounds. BOA binds to the promoter of CCA1 through newly identified promoter binding sites and activates the transcription of CCA1 in vivo and in vitro. In transgenic Arabidopsis lines that overexpress BOA, the period length of CCA1 rhythm was increased and the amplitude was enhanced. Rhythmic expression of other clock genes, including LHY, GIGANTEA (GI), and TIMING OF CAB EXPRESSION1 (TOC1), was altered in transgenic lines that overexpress BOA. Rhythmic expression of BOA was also affected in mutant lines of toc1-1, gi-3, and gi-4. Results from these studies indicate that BOA is a critical component of the regulatory circuit of the circadian clock.
Subject(s)
Arabidopsis Proteins/genetics , Arabidopsis/genetics , Circadian Clocks , Flowers/metabolism , Promoter Regions, Genetic , Transcription Factors/genetics , Arabidopsis/metabolism , Arabidopsis Proteins/metabolism , DNA-Binding Proteins/metabolism , Flowers/genetics , Flowers/growth & development , Gene Expression Regulation, Plant , Photoperiod , Plants, Genetically Modified/genetics , Plants, Genetically Modified/metabolism , Transcription Factors/metabolism , TransgenesABSTRACT
Commercially improved crop performance under drought conditions has been challenging because of the complexity of the trait and the multitude of factors that influence yield. Here we report the results of a functional genomics approach that identified a transcription factor from the nuclear factor Y (NF-Y) family, AtNF-YB1, which acts through a previously undescribed mechanism to confer improved performance in Arabidopsis under drought conditions. An orthologous maize transcription factor, ZmNF-YB2, is shown to have an equivalent activity. Under water-limited conditions, transgenic maize plants with increased ZmNF-YB2 expression show tolerance to drought based on the responses of a number of stress-related parameters, including chlorophyll content, stomatal conductance, leaf temperature, reduced wilting, and maintenance of photosynthesis. These stress adaptations contribute to a grain yield advantage to maize under water-limited environments. The application of this technology has the potential to significantly impact maize production systems that experience drought.
