Anthocyanin Accumulation in Black Kernel Mutant Rice and its Contribution to ROS Detoxification in Response to High Temperature at the Filling Stage

Abstract

Effect of high temperature (HT) on anthocyanin (ANS) accumulation and its relationship with reactive oxygen species (ROS) generation in color rice kernel was investigated by using a black kernel mutant (9311bk) and its wildtype (WT). 9311bk showed strikingly higher ANS content in the kernel than WT. Just like the starch accumulation in rice kernels, ANS accumulation in the 9311bk kernel increased progressively along with kernel development, with the highest level of ANS at kernel maturity. HT exposure evidently decreased ANS accumulation in 9311bk kernel, but it increased ROS and MDA concentrations. The extent of HT-induced decline in kernel starch accumulation was genotype-dependent, which was much larger for WT than 9311bk. Under HT exposure, 9311bk had a relatively lower increase in ROS and MDA contents than its WT. This occurrence was just opposite to the genotype-dependent alteration in the activities of antioxidant enzymes (SOD, CAT and APX) in response to HT exposure, suggesting more efficiently ROS detoxification and relatively stronger heat tolerance for 9311bk than its WT. Hence, the extent of HT-induced declines in grain weight and kernel starch content was much smaller for 9311bk relative to its WT. HT exposure suppressed the transcripts of OsCHS, OsF3’H, OsDFR and OsANS and impaired the ANS biosynthesis in rice kernel, which was strongly responsible for HT-induced decline in the accumulation of ANS, C3G, and P3G in 9311bk kernels. These results could provide valuable information to cope with global warming and achieving high quality for color rice production.

The Potential of High-Anthocyanin Purple Rice as a Functional Ingredient in Human Health

“…Therefore, most literature reviews tend to focus on the roles of anthocyanins in enhancing tolerance to abiotic and biotic stresses. Zaidi et al, 2019 showed that high temperature during grain development resulted in declines in grain weight and kernel starch content, and a mutant rice plant displaying grain anthocyanin production was much less damaged by high temperatures compared to wild-type plants without grain anthocyanin pigmentation [ 146 ]. In addition, anthocyanin has been used to distinguish drought-responsive traits.…”

Recent Insights into Anthocyanin Pigmentation, Synthesis, Trafficking, and Regulatory Mechanisms in Rice (Oryza sativa L.) Caryopsis

“…High temperature induces an alteration in the expression of CHS, F3H, DFR, and ANS genes in rice and hinders anthocyanin synthesis, resulting in decreasing accumulation of anthocyanin in the rice caryopsis. A daily mean temperature of about 32 °C compared to that of 22 °C can result in a reduction of more than 20% in the amount of anthocyanin during grain filling [ 138 ]. Kim and co-workers [ 69 ] reported that the expression level of CHS, F3H, DFR, ANS, and AN5 of the Heugjinju black rice cultivar was 200–500-fold lower for plants grown under 21 °C compared to those grown under 27 °C.…”

A rice R2R3‐MYB (OsC1) transcriptional regulator improves oxidative stress tolerance by modulating anthocyanin biosynthesis

“…A positive correlation was also observed between OsC1 expression and late ABP genes. Transcript abundance of F3H, DFR and ANS have been reported in colored rice variety compared to white rice variety at 7 DAP (Kim et al, 2007;Zaidi et al, 2019). We also speculate that OsC1 could be an activator of anthocyanins/flavonoids-related genes such as F3 0 H/DFR/ANS.…”