A Metallochaperone HIPP33 Is Required for Rice Zinc and Iron Homeostasis and Productivity

Abstract

Both zinc (Zn) and iron (Fe) are essential micro-nutrients for plant growth and development, yet their levels in plants are tightly regulated to prevent either deficiency or phytotoxicity. In agronomic reality, such an imbalance of metal bioavailability to crops occurs frequently. Thus, mining genetic resources to improve crop traits relevant to metal homeostasis is a great challenge to ensure crop yield and food quality. This study functionally identified an uncharacterized metallochaperone family HIPP protein gene Heavy Metal Associated Isoprenylated Plant Proteins 33 (OsHIPP33) in rice (Oryza sativa). OsHIPP33 resides in the nucleus and plasma membrane and constitutively expresses throughout the lifespan. Transcription of OsHIPP33 is not induced by deprivation of Zn and Fe but upregulated under excessive Zn and Fe stress. In a short-term (one month) hydroponic study with the normal Zn and Fe supply, there were no significant changes in the growth and metal accumulation between the knockout (OsHIPP33) or knockdown (RNA interference) mutant lines and wild-type, while the long-term field trials (for two successive years) demonstrated that the mutation of OsHIPP33 significantly compromised the rice growth and development (such as rice leave tissues, panicle length, spikelet fertility, seed weight per plant, 1000-grain weight, etc.), with the mature grain yield of OsHIPP33 and RNAi lines reduced by 52% and 12–15% respectively, compared with wild-type. Furthermore, the accumulation of Zn and Fe in rice straw, husk and brown rice was also reduced. These results suggest that the disruption of OsHIPP33 can dampen rice agronomic traits, signifying that OsHIPP33 expression is required for Zn and Fe homeostasis and subsequent production of rice grains.

A Metal Chaperone Gene Regulates Rice Growth and Seed Development by Manganese Acquisition and Homeostasis

“…OsHIPP56 may co-work with the transporters to play that role. Our previous study showed that OsHIPP56 is expressed dominantly in node I, leaf blade, and husk [30], this pattern of OsHIPP56 expression could support the assumption that OsHIPP56 would function with some metal transporters to deliver Mn into seeds. Further investigation on the mechanisms for Mn accumulation in rice grains will be required.…”

“…OsATX1 plays an important role in Cd and Cu homeostasis [29]. OsHMP chelates Cd and Mn [26] and OsHIPP33 regulates homeostasis of Zn and Fe [30]. To functionally investigate OsHIPP56, the transcriptional expression of OsHIPP56 under Mn deficiency and excess was first characterized.…”

An investigation of zinc isotope fractionation in cacao (Theobroma cacao L.) and comparison of zinc and cadmium isotope compositions in hydroponic plant systems under high cadmium stress

“…A Faraday collector configuration that employed the L5, L3, Ax, H2, H3 and H4 cups was used for the analyses, with all collectors fitted with 10 11 Ω resistors. Faraday collectors L3, Ax, H2 and H4 were employed to measure the ion beams of 64 Zn, 66 Zn, 67 Zn and 68 Zn, while L5 and H3 were used to monitor 62 Ni and 135 Ba 2+ to allow for spectral interference corrections of isobaric Ni + and Ba 2+ ions on the different Zn isotopes. Each sample measurement entailed three blocks of twenty 5 s integration cycles, with electronic baselines measured for 15 s prior to each block, during which the ion beam was deflected in the electrostatic analyser 52 .…”

“…In the following, all δ 66 Zn values are reported relative to the JMC-Lyon Zn isotope standard. To this end, the initial results were corrected for a δ 66 Zn offset of + 0.28‰ for AA-ETH Zn relative to JMC-Lyon Zn 54 .…”

“…The level of significance for the ANOVA test was set at p < 0.05. Further ANOVA and Kruskal-Wallis tests were conducted for the dry biomass (g), Zn concentrations (mg kg −1 ) and δ 66 Zn values of the cacao organs from the 19 genotypes, with the level of significance also set at p < 0.05. The coefficient of determination (R 2 ) was calculated for the dry biomass (g), Zn concentrations (mg kg −1 ) and δ 66 Zn values of the 19 cacao genotypes.…”