Very high sensitivity of African rice to artificial ultraviolet-B radiation caused by genotype and quantity of cyclobutane pyrimidine dimer photolyase

Abstract

Ultraviolet-B (UVB) radiation damages plants and decreases their growth and productivity.We previously demonstrated that UVB sensitivity varies widely among Asian rice (Oryza sativa L.) cultivars and that the activity of cyclobutane pyrimidine dimer (CPD) photolyase, which repairs UVB-induced CPDs, determines UVB sensitivity. Unlike Asian rice, African rice (Oryza glaberrima Steud. and Oryza barthii A. Chev.) has mechanisms to adapt to African climates and to protect itself against biotic and abiotic stresses. However, information about the UVB sensitivity of African rice species is largely absent. We showed that most of the African rice cultivars examined in this study were UVB-hypersensitive or even UVB-super-hypersensitive in comparison with the UVB sensitivity of Asian O. sativa cultivars. The difference in UVB resistance correlated with the total CPD photolyase activity, which was determined by its activity and its cellular content. The UVB-super-hypersensitive cultivars had low enzyme activity caused by newly identified polymorphisms and low cellular CPD photolyase contents. The new polymorphisms were only found in cultivars from West Africa, particularly in those from countries believed to be centres of O. glaberrima domestication. This study provides new tools for improving both Asian and African rice productivity.Plants use sunlight for photosynthesis and are therefore exposed to ultraviolet-B (UVB) radiation (280-315 nm). Damage caused by UVB radiation decreases plant growth and productivity 1 . Artificial UVB radiation in a growth chamber or field can also damage plants, decreasing the growth and productivity of economically important crops, including rice; UV radiation exclusion prevents such damage and can increase plant growth 2,3 .Rice is one of the most important staple grains globally and is extensively cultivated worldwide in regions with different climates. The genus Oryza comprises 22 wild species and 2 species of cultivated rice (Oryza sativa L. and O. glaberrima Steud.); O. sativa and O. glaberrima originated from and were domesticated in Asia and West Africa, respectively 4,5 . Asian rice cultivars belong to one of the two major O. sativa subspecies, japonica or indica. UVB sensitivity varies widely among Asian rice cultivars 6 due to differences in the enzymatic activity for repair of UV-induced DNA damage 7 . Upon UVB irradiation, cyclobutane pyrimidine dimers (CPDs) are formed between adjacent pyrimidines on the same DNA strand 8 . In the photoreactivation pathway, the enzyme photolyase absorbs light in the UVA (315-400 nm) and blue ranges through the FAD chromophore, which releases energy to induce dimer dissociation into monomers 9 . Photoreactivation activity is higher in the UVB-resistant rice cultivar Sasanishiki (O. sativa ssp. japonica) than in the less resistant cultivar Norin 1 (also japonica) 10 . The higher activity in Sasanishiki results from spontaneous mutations in the CPD photolyase gene that alter the function of the enzyme rather than from a regulatory mutation 11 . The ...

UV‐B signalling in rice: Response identification, gene expression profiling and mutant isolation

“…Hidema and co‐workers investigated UV‐B‐induced reduction of shoot dry weight and tiller number in various Oryza species and indexed their UV‐B stress sensitivity (Hidema & Kumagai, 2006; Iwamatsu et al, 2008; Mmbando, Teranishi, & Hidema, 2020). It is noted that the extent of UV‐B‐induced growth response (Figures 3 and 4) is partially correlated with the UV‐B stress sensitivity.…”

“…The japonica cultivar Sasanishiki, which showed the greatest growth response (Figure 3a), was least sensitive (i.e., most resistant) to UV‐B stress (Teranishi, Iwamatsu, Hidema, & Kumagai, 2004). On the other hand, the above‐mentioned two African species, which showed no growth response, were recorded to have high stress sensitivity, that is, low resistance, to UV‐B stress (Mmbando et al, 2020). The UV‐B signalling underlying the growth response might be involved in the establishment of UV‐B‐stress resistance.…”

“…We compared the phylogenetic tree of Oryza with the growth data shown in Figures 2-4 (Figure S3). The xed their UV-B stress sensitivity (Hidema & Kumagai, 2006;Iwamatsu et al, 2008;Mmbando, Teranishi, & Hidema, 2020). It is noted that the extent of UV-B-induced growth response (Figures 3 and 4) is partially correlated with the UV-B stress sensitivity.…”

The trade-off between UVB sensitivity and tolerance against other stresses in African rice species

“…Recently, Mmbando et al (2020) japonica, Sasanishiki), sensitive (O. sativa ssp. japonica, Norin 1), and hypersensitive (O. sativa ssp.…”

β-Sitosterol differentially regulates key metabolites for growth improvement and stress tolerance in rice plants during prolonged UV-B stress

“…Given the fact that UV-B stress can negatively affect numerous morpho-physiological events and metabolic profile in different plant species as reported in earlier studies [ 3 , 19 ]. Notably, rice cultivars also show extreme sensitivity to UV-B light [ 20 ], and thus, more efforts are required in finding ways to improve resistance and maintain high productivity of rice. Recent efforts to enhance rice tolerance for UV-B stress are largely associated with transgenic approaches [ 12 , 21 , 22 ].…”