An iron-deficiency tolerant genotype of sorghum effectively localizes iron to the thylakoid membranes of the bundle sheath cells

ABSTRACT

Although sorghum (Sorghum bicolor L.), a C₄ grass plant, requires a higher iron (Fe) concentration in its leaves for sufficient growth compared to C₃ grass plants, there are differences in Fe-deficiency tolerance among sorghum genotypes. C₄ plant sorghum localizes Fe in bundle sheath (BS) cells as a major site for CO₂ assimilation; however, the response of chloroplasts in BS cells to Fe deficiency remains unknown. We compared the allocation of Fe and proteins involved in the photosystems between Fe-deficiency-tolerant and Fe-deficiency-susceptible sorghum genotypes. The distribution patterns of the Fe-requiring core proteins of photosystems I and II were the same in both genotypes, whereas the tolerant genotype, line D100, allocated more Fe to the BS thylakoid membranes than the susceptible genotype, regardless of Fe nutritional status and leaf Fe content. These results suggest that the tolerant D100 sorghum line has mechanisms to supply sufficient Fe to the BS thylakoid membranes.

KEY WORDS:

• Bundle sheath
• iron (Fe)
• photosystems
• sorghum
• thylakoid membrane

Acknowledgments

The authors thank Mr. Junichi Yoneda and Mr. Tsuyoshi Tokunaga (EARTHNOTE Co., Ltd.) for providing sorghum lines.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/00380768.2024.2358120

Additional information

Funding

This research was funded by EARTHNOTE Co., Ltd. and JSPS KAKENHI (grant number 20H02891) granted to K.H.