Location: Sustainable Agricultural Systems Laboratory
2019 Annual Report
Objectives
Objective 1: Identify metabolic pathways and nutrient molecules that are impacted by cold, heat, and drought stress in tomato. [NP301, C3, PS3A]
Objective 2: Determine the mineral and nutritional metabolite composition of field-grown legume and some non-legume cover crops, and determine how their constituents modify tomato stress tolerance – cold, heat, drought, and yield – using existing transgenic or mutant tomato lines. [NP301, C3, PS3A; C1, PS1A]
Objective 3: Determine how plant responses to cold, heat, and drought are modified at the transcript level in tomato by the hyperaccumulation of polyamines and/or the reduction of the stress hormones, ethylene and methyl jasmonate. [NP301, C3, PS3A]
Approach
Utilize previously developed genetically engineered tomato genotypes - two that have fruit ripening-specific accumulation of polyamines spermidine and spermine (Spd-Spm), other two that constitutively-express spermidine, one that is 50% reduced in fruit-ripening hormone ethylene (Eth-def), another that is deficient in the stress hormone methyl jasmonate (JAS-def), a cross between Eth-def and Spd-Spm, and a cross between JAS-def and Spd-Spm – and test them for tolerance against abiotic stresses such as drought, heat, and cold, and yield. Analyses for water use efficiency (WUE), gene medleys, nutrient content, yield, fruit quantity and quality, metabolic pathways, and gene networks will be defined. In addition, field-grown legume and non-legume cover crops will be analyzed for their levels of metabolites and biomolecules just before flowering time to provide a lead into their utilization for imparting field-based resistance against abiotic stresses in field-grown tomato genotypes.
Progress Report
Tomato is one of the major vegetables in regards to consumption and its production volume in the world, being cultivated on an area of approximately 4.8 million hectares with an annual production of 182 million tonnes. It is an established model system for studying fleshy fruits, developing novel information on ripening and senescence of fruits, and understanding the role of the ripening hormone ethylene as well as important signal transduction pathways because it is amenable to genetic and molecular dissection. In addition to finding mechanisms to increase fruit yield and longer shelf life, the consumer recognition of fruits as sources of health-promoting nutrients for a healthier life has intensified research on tomato. Moreover, plants are sessile, and therefore constantly exposed to environmental extremes, including diverse abiotic and biotic stressors that impact their growth, yield and nutritional quality. Our understanding of responses of tomato to these vagaries of nature is at best pedestrian and the identification of genetic and biochemical determinants of stress pathways are, therefore, important to research paving the way for development of new tomato germplasm that can withstand these stresses minimizing losses in yield. We are focusing our research studies on the combinatorial role(s) of plant hormones in enhancing nutrient load and stress tolerance in tomato.
Plant hormones are major cellular signaling molecules that modulate growth, development and respond to internal and external cues in plants. Nine plant hormones are now recognized, and their perception, intra- and inter-cellular movement/communication, and interaction with receptors and gene regulators is better understood now than before. However, intricate mechanistic details are yet to be discovered. Each plant hormone has a unique/specific function and also regulates networks of other hormones via cross talks involving specific transcription factors and small Ribonucleic acid (RNAs). This new knowledge has brought to light the fact that the regulation of plant physiological processes involves a complex cross-talk among different hormones. The salient features of hormone biology are considered important in understanding cross talks between hormones necessary for developing stress-resistant germplasm.
Plant hormones we are studying include a group of low molecular weight organic cations called polyamines. Polyamines consist of putrescine, spermidine, spermine and T-spermine. The latter three polyamines being implicated in regulating plant growth, inhibiting senescence and stress responses of plants. Our experiments over this reporting period led to the finding that the polyamine spermidine influences floral organ identity and fruit set in tomato; involving the genetic program(s) that control the expression of homeotic genes likely via gibberellin (GA) signaling. These studies suggest a nexus between polyamines and developmental programs in plants. We also identified and characterized 13 gene members of lipoxygenase (LOX), an enzyme that is critical for the synthesis of methyl jasmonate stress hormones. Additionally, we identified LOX genes that responded positively or negatively in tomato during drought and salt stress. These data are important for genetic manipulation and development of abiotic stress resistance in plants.
Accomplishments
1. Metabolic switch for flower development and fruit/seed set in tomato discovered. In separate collaborations between ARS scientists in Beltsville, Maryland, and the Purdue University (Indiana) and Adams Mickiewicz University (Poland) it was demonstrated that (i) the catabolism of polyamines determines the rate at which senescence can progress in plants, and (ii) the polyamine spermidine positively impacts floral organ identity and fruit/seed set in tomato. The novel information unearthed by this research is useful to academicians (scientists and students) and industry researchers around the world involved in containing senescence of plants and enhancing floral development for setting good seeds and fruit not only in tomato but also other plants.
Review Publications
Anwar, R., Mattoo, A.K., Handa, A.K. 2019. Postharvest Biology and Nanotechnology. New Jersey: Wiley Publishers. 403 p.
Paliyath, G., Mattoo, A.K., Handa, A.K., Shetty, K., Wilson, C. 2019. Enhancing food security through postharvest technology - Current and future perspectives. In: Paliyath, G., Subramanian, J., Loong-Tak, L., Subramanian, K.S., Handa, A.K., Mattoo, A.K., editors. Postharvest Biology and Nanotechnology. Hoboken, NJ: Wiley Publishers. p. 1-13.
Mattoo, A.K., Sobieszczuk-Nowicka, E. 2018. Polyamine as signaling molecules and leaf senescence. In: Sarwat, M., Tuteja, N., editors. Senescence Signalling and Control in Plants. New York, NY: Elsevier. p. 125-138.
