Drought Stress Inhibits Starch Accumulation in Taro (Colocasia esculenta L. Schott).

BACKGROUND: Colocasia esculenta L. Schott is a main traditional root crop in China, serving as an important vegetable and staple food. Drought stress plays vital role on the growth and development of taro corm. METHODS: Two different varieties of taro in Jiangsu were selected: Xiangsha taro and Longxiang taro. The accumulation characteristics, morphological structure, and physicochemical properties of taro corm starch were studied by microscopic observation, particle size analysis, and X-ray diffractometer (XRD) analysis. Transcriptome analyses were used to identify the related genes of taro corm under drought stress. RESULTS: During the growth of taro, the number of amyloplasts showed an obvious increasing trend and shifted from being dispersed throughout the cells to being gathered on one side of the cells, and morphological observations showed that smaller granular distribution gradually changed to a larger lumpy distribution. The particle size of Longxiang taro is smaller than that of Xiangsha taro. Under drought stress conditions, the occurrence of starch grains and corm size were inhibited in Xiangsha taro. Transcriptome sequencing of drought-stressed taro corms showed that the enzymes related to starch synthesis were differentially expressed. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of drought-stressed taro corms showed that drought affected hormone signal transduction, material metabolism, drought stress tolerance, plant growth and development, and stress resistance, which triggered the plant drought adaptive response. CONCLUSIONS: Drought stress inhibits starch accumulation in taro.

Encoded C4 homologue enzymes genes function under abiotic stresses in C3 plant.

Plant organisms assimilate CO2 through the photosynthetic pathway, which facilitates in the synthesis of sugar for plant development. As environmental elements including water level, CO2 concentration, temperature and soil characteristics change, the plants may recruit series of genes to help adapt the hostile environments and challenges. C4 photosynthesis plants are an excellent example of plant evolutionary adaptation to diverse condition. Compared with C3 photosynthesis plants, C4 photosynthesis plants have altered leaf anatomy and new metabolism for CO2 capture, with multiple related enzymes such as phosphoenolpyruvate carboxylase (PEPCase), pyruvate orthophosphate dikinase (PPDK), NAD(P)-malic enzyme (NAD(P)-ME), NAD(P) - malate dehydrogenase (NAD(P)-MDH) and carbonic anhydrases (CA), identified to participate in the carbon concentrating mechanism (CCM) pathway. Recently, great achievements about C4 CCM-related genes have been made in the dissection of C3 plant development processes involving various stresses. In this review, we describe the functions of C4 CCM-related homologous genes in carbon and nitrogen metabolism in C3 plants. We further summarize C4 CCM-related homologous genes' functions in response to stresses in C3 plants. The understanding of C4 CCM-related genes' function in response to abiotic stress in plant is important to modify the crop plants for climate diversification.

The sucrose transport regulator OsDOF11 mediates cytokinin degradation during rice development.

Photosynthetic tissues are dynamic structures whose homeostasis depends on the coordination of two antagonistic processes: self-maintenance and supporting sink tissues. The balance of these processes determines plant development, which might be mediated by cytokinin. However, little is known about the link between sucrose transport signaling and cytokinin. Rice (Oryza sativa) DNA BINDING WITH ONE FINGER11 (OsDOF11) is a transcription factor that mediates sucrose transport by inducing the expression of sucrose transporter genes. Here, we found that OsDOF11 loss-of-function mutants showed a semi-dwarf phenotype with a smaller cell length due to increased cytokinin content in source tissues. RNA sequencing and reverse transcription quantitative PCR analyses revealed that genes involved in cytokinin signaling and metabolism were affected in osdof11 mutants. Yeast one-hybrid, dual-luciferase reporter, and chromatin immunoprecipitation experiments showed that OsDOF11 directly binds to the promoter regions of O. sativa CYTOKININ OXIDASE/DEHYDROGENASE4 (OsCKX4). Moreover, mutation of osckx4 in the osdof11 osckx4 double mutant rescued the semi-dwarf phenotype of the osdof11 mutant. Interestingly, exogenous application of kinetin promoted OsDOF11 expression earlier than OsCKX4, and overexpression of O. sativa VIN3-LIKE 2 caused an increase in active cytokinin levels and induced OsDOF11 transcript levels. Taken together, our results suggest a model in which both a sucrose transport regulator (OsDOF11) and cytokinin via OsCKX4 establish a feedback loop to maintain dynamic tissue homeostasis.