Location: Sustainable Agricultural Systems Laboratory
2020 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
Fruits and vegetables are sources of dietary micronutrients, vitamins and antioxidants for daily human consumption. Tomato is one of the major vegetables regarding its consumption and its production volume in the world, being cultivated on an area of approximately 4.8 million hectares with an annual yield of 182 million tons. Tomato is an established model system, used for developing novel information on ripening and senescence of fleshy fruits. Moreover, ripening of tomatoes leads to production of nutrients. Therefore, significant effort is directed toward understanding the genetic regulation of the tomato ripening process and the role of hormones, ethylene in particular, as well as the signal transduction pathways. In addition to finding mechanisms to increase fruit yield and longer shelf life, consumer recognition of fruits as sources of health-promoting nutrients for a healthier life has intensified research on tomato. Tomato plants being sessile, are constantly exposed to environmental extremes, including diverse abiotic and biotic stressors, which impact their growth, yield and nutritional quality. Our project goals include identification of genetic and biochemical determinants of stress pathways to pave the way for the development of new tomato germplasm that can withstand abiotic stresses and minimize yield losses. Our research studies are also focused on the combinatorial role(s) of plant hormones in enhancing nutrient load and stress tolerance in tomato. Although a plethora of genes and proteins have been implicated in tomato fruit ripening, developing fruits to have longer shelf life without compromising the nutrient content has yet to be achieved.
It has become clear that the regulation of plant physiological processes involves a complex crosstalk 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 ethylene, jasmonic acid and a group of low molecular weight organic cations called polyamines, namely, putrescine, spermidine, spermine and T-spermine. These four polyamines have been implicated in regulating plant growth, and inhibiting senescence and stress responses of plants.
For Objective 1 we characterized numerous novel tomato heat shock protein (HSP) genes which are expressed at the transition of the mature green tomato fruit into the ripening process. HSPs are ubiquitous and highly conserved in nature. Heat stress upregulates their gene expression and now it is known that they are also developmentally regulated. During this reporting period we identified two additional small HSP genes, SlHSP17.7A and SlHSP17.7B, localized on tomato chromosome 6 and chromosome 9, respectively. Further, we demonstrated that ethylene hormone and a previously characterized master regulator known as RIN (Ripening Inhibitor) transcription factor crosstalk to regulate these HSP genes. These findings are novel and should help develop new strategies to produce tomato germplasm with prolonged postharvest shelf life along with resistance to heat. One manuscript was written and submitted for publication.
For Objective 2 we planned the second year of field experiments designed to determine the impact of legume cover crops on the accumulation of important biomolecules that provide resistance against abiotic stress. Data on the first year of field work has been analyzed. A draft of a manuscript on ionome and metabolome of vetch and rye cover crops foliage will be initiated when the data analyses have been statistically evaluated.
For Objective 3 we demonstrated that tomato responses to abiotic stresses are unique to each stress. For example, the tomato response to heat was found to be different, in fact, opposite to the response to cold regarding the genes impacted. Also, our other studies determined interactions between transcription factors and ethylene in regulating tomato responses to heat shock protein genes. Our intent is to determine and unravel genetic switches that would be useful for developing a longer lasting, nutrient rich and heat tolerant tomato germplasm. One manuscript has been drafted and is currently with our collaborator at Purdue University for comment.
Accomplishments
1. Novel small heat shock protein genes identified that have potential role in fruit ripening. Fruit ripening genes identified. ARS scientists in Beltsville, Maryland have identified and characterized small heat shock protein genes that work with the fruit ripening hormone ethylene to start the ripening process in tomato. Now scientists and breeders can design and develop new heat-resistant tomato germplasm. This information is also useful to molecular biologists and plant breeders developing heat-stress resistant tomatoes.
Review Publications
Van Der Straeten, D., Kanellis, A., Kalaitzis, P., Bouzayen, M., Chang, C., Mattoo, A.K., Zhang, J. 2020. Ethylene biology and beyond: Novel insights in the ethylene pathway and its interactions. Frontiers in Plant Science. 11:248. https://doi.org/10.3389/fpls.2020.00248.
Sobieszczuk-Nowicka, E., Paluch-Lubawa, E., Mattoo, A.K., Jelonek, M.A., Gregersen, P.L., Pacak, A. 2019. Polyamines - a new metabolic switch: Crosstalk with networks involving senescence, crop improvement, and mammalian cancer therapy. Frontiers in Plant Science. 10:1-12. https://doi.org/10.3389/fpls.2019.00859.
Nambeesan, S., Mattoo, A.K., Handa, A.K. 2019. Nexus between spermidine and floral organ identity and fruit/seed set in tomato. Frontiers in Plant Science. https://doi.org/10.3389/fpls.2019.01033.
Roberts, D.P., Mattoo, A.K. 2019. Sustainable crop production systems and human nutrition. Frontiers in Sustainable Food Systems. https://doi.org/10.3389/fsufs.2019.00072.
Upadhyay, R.K., Handa, A.K., Mattoo, A.K. 2019. Genome-wide expression dynamics of tomato (Solanum lycopersicum L.) 9- and 13-lipoxygenases identify family members with differential regulation in response to common abiotic stresses. Genes. https://doi.org/10.3390/genes10090683.
Mattoo, A.K., Upadhyay, R.K. 2019. Plant hormones - Some glimpses on biosynthesis, signaling networks and cross talk. Book Chapter. In: Sensory Biology of Plants, Springer pp. 227-246.
Anwar, R., Fatima, T., Mattoo, A.K. 2019. Tomatoes - A model crop of solanaceous plants. Oxford University Press. p. 1-50. https://doi.org/10.1093/acrefore/9780199389414.013.223.
Anwar, R., Fatima, S., Mattoo, A.K., Handa, A.K. 2019. Fruit architecture in polyamine-rich tomato germplasm as influenced by a medley of cell cycle, cell expansion and fruit shape genes. Plants. https://doi.org/10.3390/plants8100387.
