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Published: 2022-09-14

How plants protect themselves from strong light

NEWS A new study at Umeå University uncovers a new mechanism for how plants protect themselves from strong illumination.

Text: Per Melander

Jingfang Hao, senior research engineer at the Department of Plant Physiology at Umeå University, says that the photoprotection they studied here is a biological process named non-photochemical quenching (NPQ), which plants carry out to dissipate the excess absorbed light as heat under strong illumination.

"The negative regulation of this photoprotection is mediated by a chloroplast membrane-anchored protein, SUPPRESSOR OF QUENCHING 1 (SOQ1). SOQ1 consists of a stromal domain, transmembrane domain and lumenal domain containing thioredoxin-like (Trx-like), NHL domain and C-terminal domain (CTD)", says Jingfang Hao and continues:

"The previous study determined that Trx-like domain is essential for SOQ1 suppression function on photoprotection. We discovered that besides Trx-like domain, CTD is indispensable for the negative regulation of photoprotection. The mechanism is that CTD can accept the electron from Trx-like domain and donate the electron to inhibit the target protein required for NPQ".

Why is this an important finding?

"Because this is the first study to report the crystal structure of SOQ1 lumenal domain and determine the function of the C-terminal domain of SOQ1 protein. Our findings uncover a new mechanism that how plants protect themselves from strong illumination".

Jingfang Hao tells further that investigating the localization of SOQ1, she isolated the chloroplast sub-fractions such as intact thylakoids, thylakoid membranes and lumen.

"I was surprised to find SOQ1 can be cleaved as several truncated forms in the lumenal fraction. Our Chinese colleagues also found these truncated forms when they purified the SOQ1 lumenal domains from bacteria. These findings suggest that the truncated forms could play some physiological functions".

What use will your findings have?

"The structure of the SOQ1 lumenal domain can provide a reference for the researchers to study similar proteins or proteins containing similar domains in other species. Moreover, our findings give a contribution to understanding how plants adapt the stressful environments".