Arsenic Stress Responses and Accumulation in Rice

Abstract

Rice (Oryza sativa L.) is one of the world’s most vital staple grains, and 90% of it is produced and consumed in Asia alone. It plays a significant role in the entry of mineral nutrients into the food chain. Arsenic (As) is a toxic heavy metal that threatens the major rice-growing regions in the world, particularly in Asia. Arsenic is ubiquitously present in moderate concentrations in the environment because of natural geological processes and anthropogenic impacts. However, rapid industrialization and excessive use of arsenic-rich groundwater are further fueling the increased arsenic concentration in agricultural topsoil. Arsenic accumulation in rice plants has a significant adverse effect on plant, human, and livestock health. Although arsenic contamination in rice is well documented, its interaction and accumulation in rice are poorly understood. So far, no candidate genes or QTLs associated with arsenic interaction are used in breeding programs for the development of low-arsenic-accumulating rice varieties. The development and adaptation of new low-arsenic-accumulating rice cultivars resilient to arsenic toxicity constitute safe ways to mitigate arsenic contamination in rice. Recent scientific advances in rice genetics, genomics, and physiology have opened up new opportunities to speed up the process of developing low-arsenic-accumulating rice cultivars for the rapidly growing human population.

Toxic Metals and Metalloids in Hassawi Brown Rice: Fate during Cooking and Associated Health Risks

“…Although cadmium contamination in rice is within safe limits, it is at the marginal level and nearly approaching the upper safe limit. Arsenic contamination in rice is a natural process, particularly if arsenic-contaminated water is used for irrigation or the soil itself has a high load of arsenic due to the nature of rock formation [47]. It has already been proven that, under rice-growing conditions, arsenic is readily converted into arsenite, thereby enhancing the accumulation of arsenic in rice grains by up to 10-fold as compared to other staple crops [13,48].…”

Identification of Promising Genotypes Through Systematic Evaluation for Arsenic Tolerance and Exclusion in Rice (Oryza sativa L.)

“…Carcinogenic arsenic accumulation in rice plants damages tissue and disrupts cellular homeostasis. As toxicity in rice plants has a cascade effect that includes preventing the most sensitive germination phase, limiting cell division, elongation of the primary roots, stunted development, and, finally, grain accumulation (Suriyagoda et al, 2018;Murugaiyan et al, 2021). As absorption by the roots and transport to the leaves via the transpiration stream via xylem resulting in a toxic As load in plant tissues (Tang et al, 2020).…”

“…In natural waters and paddy topsoil, inorganic As exists in two main species forms, namely, more toxic trivalent arsenite As (III) and less toxic pentavalent arsenate As (V) (Abedin et al, 2002b). In irrigated lowland submerged paddy soils (anaerobic conditions), As predominantly exists as oxyanions of reduced arsenite As (III) and in rainfed upland paddy soils (aerobic conditions), oxidized arsenate As (V) dominates (Suriyagoda et al, 2018;Murugaiyan et al, 2021). Since rice plants do not possess any natural As transporters or have lost them during the domestication process, their uptake and translocation depend on exploiting closely resembling nutrients (Sahoo and Mukherjee, 2014).…”

“…This switch between species is likely to be influenced by water availability, As bioavailability in soil, and the presence of microbial activity. Although As interaction with rice has been well recognized over the past two decades, its genotypic variations, the most significant tolerant varieties, screening strategies, and accumulation are poorly understood (Murugaiyan et al, 2021). So far, no donor germplasm associated with As exclusion has been identified or used in breeding programs for the development of As-excluding rice varieties.…”

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“…Arsenate As (V) can substitute for inorganic phosphate in a variety of biochemical processes that affect key metabolism in the cell. In contrast, As (III) having high affinity toward sulfhydryl-containing enzymes interferes with key enzymes in a deleterious way (Murugaiyan et al, 2021).…”