Characterization of low Ca2+ stress-induced embryo apoptosis response genesand their regulation of embryo development

H Chen et al., 'Characterization of low Ca2+ stress-induced embryo apoptosis response genesand their regulation of embryo development', pp.P-056, 2018

Ca2+ deficiency in soil induces early embryo abortion in peanut,producing empty pods, or ill-filled pods, especially underdrought condition, which is a general problem. However, theunderlying mechanism remains unclear. In this study, embryoabortion was characterized to be caused by apoptosis markedwith cell wall degradation. Using a method of SSH cDNA librariesassociated with library lift (SSHaLL), 62 differentiallyexpressed genes were isolated from young peanut embryos,which were classified to be stress responses, catabolic process,carbohydrate and lipid metabolism, embryo morphogenesis,and regulation. The cell retardation with cell walldegradation was caused by up-regulated cell wall hydrolasesand down-regulated cellular synthases genes. Two CYP707A4genes, encoding abscisic acid (ABA) 8?-hydroxylases, key enzymesfor ABA catabolism, were up-regulated by 21-fold underCa2+-deficient conditions, reducing the ABA level in early embryos.Over-expression of AhCYP707A4 in Nicotiana benthamianashowed a phenotype of low ABA content with high numbersof aborted embryos, small pods and less seeds, which confirmsthat CYP707A4 is a key player in regulation of Ca2+ deficiency-inducedembryo abortion via ABA-mediated apoptosis. Theresults elucidated the mechanism of low Ca2+-induced embryoabortion. A set of varieties with different sizes of pods were evaluatedfor their tolerance to calcium stress, and we found thatbig pod varieties showed less tolerance to low calcium and moreeasy to produce ill-filled pods or empty pods. Drought will makeworse of the phenomenon. Soil supplied with rich calcium willimprove the pods filling and greatly reduce number of emptypods. We conclude big-pod varieties easier to produce emptypods are also associated with calcium level in the soil