Seeds are highly specific organs and play a vital role in synthesizing storage materials during development and filling stages. Little is known about the physiological effects of high sunlight on nongreen seed development and storage accumulation in caster seeds. Therefore, it remains unclear if the high solar radiation can physiologically result in an increased caster seed production.
  Dr. ZHANG Yang of Xishuangbanna Tropical Botanical Garden (XTBG) and his teacher of Kunming Institute of Botany conduced a study to investigate the physiological role of light exposure on castor seed development and storage accumulation both in vivo and in vitro. In a parallel experiment, they determined the photosynthetic efficiency of capsule walls of caster which indicated that the capsule walls were photosynthetically active and contributed significantly to carbon fixation and seed yield.
   Characterization of seed development of castor under light (sun) and dark conditions (shaded) indicated increased lipid accumulation under light conditions. The researchers further substantiated the observation through experiments using seeds cultured under dark and different light intensities. Using high-throughout RNA-Seq techniques, they then delved into the molecular basis of light physiology and profiled potential pathways of the effect of light on oil accumulation in developing castor seeds at the transcriptional level . 
 The results showed that exposure to high light enhanced photosynthetic activity in seed coats and consequently increased oil accumulation. Consistent results were also reached using cultured seeds. High-throughput RNA-Seq analyses further revealed that genes involved in photosynthesis and carbon conversion in both the Calvin–Benson cycle and malate transport were differentially expressed between seeds cultured under light and dark conditions, implying several venues potentially contributing to light-enhanced lipid accumulation such as increased reducing power and CO2refixation which underlie the overall lipid biosynthesis.
   The study entitled “High light exposure on seed coat increases lipid accumulation in seeds of castor bean (Ricinus communis L.), a nongreen oilseed crop” has been published online in Photosynthesis Research.

Contact
ZHANG Yang  Ph.D
Key Laboratory of Tropical Plant Resources and Sustainable Use, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences
E-mail: pengzhang_123@163.com