Planning for food security in a changing climate.

The Intergovernmental Panel on Climate Change and other international agencies have concluded that global crop production is at risk due to climate change, population growth, and changing food preferences. Society expects that the agricultural sciences will innovate solutions to these problems and provide food security for the foreseeable future. My thesis is that an integrated research plan merging agronomic and genetic approaches has the greatest probability of success. I present a template for a research plan based on the lessons we have learned from the Green Revolution and from the development of genetically engineered crops that may guide us to meet this expectation. The plan starts with a vision of how the crop management system could change, and I give a few examples of innovations that are very much in their infancy but have significant potential. The opportunities need to be conceptualized on a regional basis for each crop to provide a target for change. The plan gives an overview of how the tools of plant biotechnology can be used to create the genetic diversity needed to implement the envisioned changes in the crop management system, using the development of drought tolerance in maize (Zea mays L.) as an example that has led recently to the commercial release of new hybrids in the USA. The plan requires an interdisciplinary approach that integrates and coordinates research on plant biotechnology, genetics, physiology, breeding, agronomy, and cropping systems to be successful.

Comparative transcriptomics as a tool for the identification of root branching genes in maize.

The root system is fundamental for plant development, is crucial for overall plant growth and is recently being recognized as the key for future crop productivity improvement. A major determinant of root system architecture is the initiation of lateral roots. While knowledge of the genetic and molecular mechanisms regulating lateral root initiation has mainly been achieved in the dicotyledonous plant Arabidopsis thaliana, only scarce data are available for major crop species, generally monocotyledonous plants. The existence of both similarities and differences at the morphological and anatomical level between plant species from both clades raises the question whether regulation of lateral root initiation may or may not be conserved through evolution. Here, we performed a targeted genome-wide transcriptome analysis during lateral root initiation both in primary and in adventitious roots of Zea mays and found evidence for the existence of common transcriptional regulation. Further, based on a comparative analysis with Arabidopsis transcriptome data, a core of genes putatively conserved across angiosperms could be identified. Therefore, it is plausible that common regulatory mechanisms for lateral root initiation are at play in maize and Arabidopsis, a finding that might encourage the extrapolation of knowledge obtained in Arabidopsis to crop species at the level of root system architecture.

Isolation and characterization of class A4 heat shock transcription factor from alfalfa.

Plant heat shock transcription factors (HSFs) regulate transcription of heat shock (HS) genes. In Arabidopsis thaliana, 21 HSFs have been classified into groups A-C. Members of class A act as typical transcriptional activators, whereas B HSFs function as coactivators or repressors depending on promoter context. The function of class C HSFs is still unclear. Here, we present the isolation and characterization of the first HSF from alfalfa (Medicago sativa L.) and designate it MsHSFA4 based on amino acid sequence analysis. The MsHSFA4 gene was determined to be single copy and was detected at two separate genetic loci in the tetraploid Medicago sativa. Overexpression of MsHSFA4 in tobacco mesophyll protoplasts resulted in weak transcriptional activity, similar to that exhibited by Arabidopsis AtHSFA4a. The MsHSFA4 proximal promoter contains three putative HSE elements, and the gene itself is activated both by heat and cold stress.

Pyramiding Mn-superoxide dismutase transgenes to improve persistence and biomass production in alfalfa.

Expression of individual superoxide dismutase (SOD) transgenes improves environmental stress tolerance and biomass production in alfalfa (Medicago sativa L.). The objective of this study was to test the hypothesis that synergy exists between transgenic SOD stress-tolerance mechanisms, specifically that the simultaneous expression of two SOD transgenes confers greater benefit than the expression of a single SOD transgene. The hypothesis was tested through an evaluation of an F(1) family generated through a sexual cross of a hemizygous Mit-MnSOD plant and a hemizygous Chl-MnSOD-transgenic alfalfa plant which had previously been screened in field trials for improved persistence. Southern analyses revealed that the parents each had single insertion regions of the MnSOD cDNA and the inheritance followed the expected Mendelian ratios. Native PAGE gels and enzyme inhibition assays revealed the activity of the transgenic MnSOD isozymes. F(1) progeny containing either the Mit-MnSOD or the Chl-MnSOD transgene had significantly higher storage organ (crown+root) biomass compared to non-transgenic siblings. The joint expression of the transgenes resulted in a numerical increase in total SOD activity. However, F(1) progeny containing both transgenes had lower shoot and storage organ biomass compared to siblings having only one or the other transgene, a result that did not support the authors' hypothesis. It was postulated that a promoter with lower expression than 35S may be necessary if closely related transgenes are to be pyramided in the same plant.