Photochemistry and proteomics of ginger (Zingiber officinale Roscoe) under drought and shading

Drought has become an increasingly serious ecological problem that limits crop production. However, little is known about the response of ginger (Zingiber officinale Roscoe) to drought and shading, especially with respect to photosynthetic electron transport. Here, differential proteomics was used to study the response of ginger to four experimental treatments: control, drought, 50% shading, and the combination of 50% shading and drought. Proteomic analysis suggested that ginger increased cyclic electron flow under drought stress by enhancing the expression of proteins related to photosystem I and cytochrome b6f. Shading significantly increased the expression of proteins related to the light harvesting complex, even under drought stress. In addition, shading increased the expression of proteins related to the oxygen evolution complex, plastocyanin, and ferredoxin-NADP(+) reductase (FNR), thereby enhancing the efficiency of photosynthetic electron utilization. The shading and drought combination treatment appeared to enhance ginger's drought tolerance by reducing the expression of FNR and enhancing cyclic electron flow. Photosynthetic and fluorescence parameters showed that drought stress caused non-stomatal limitation of photosynthesis in ginger leaves. Drought stress also significantly reduced the quantum efficiency of photosystem II (F-v/F-m), the non-cyclic electron transfer efficiency of photosystem II (phi PSII), and photochemical quenching (qP), while simultaneously increasing nonphotochemical quenching (NPQ). The addition of shading improved photosynthetic efficiency under drought. These results provide important baseline information on the photosynthetic mechanisms by which ginger responds to drought and shading. In addition, they provide a theoretical basis for the study of shade cultivation during the arid season.