Abstract
Peanut is one of the calciphilous plants. Calcium serves as a ubiquitous central hub in a large number of signaling pathways. In the field, free calcium ion (Ca2+)-deficient soil can result in unfilled pods. Four pod stages were analyzed to determine the relationship between Ca2+ excretion and pod development. Peanut shells showed Ca2+ excretion at all four stages; however, both the embryo of Stage 4 (S4) and the red skin of Stage 3 (S3) showed Ca2+ absorbance. These results showed that embryo and red skin of peanut need Ca2+ during development. In order to survey the relationship among calcium, hormone and seed development from gene perspective, we further analyzed the seed transcriptome at Stage 2 (S2), S3, and S4. About 70 million high quality clean reads were generated, which were assembled into 58,147 unigenes. By comparing these three stages, total 4,457 differentially expressed genes were identified. In these genes, 53 Ca2+ related genes, 40 auxin related genes, 15 gibberellin genes, 20 ethylene related genes, 2 abscisic acid related genes, and 7 cytokinin related genes were identified. Additionally, a part of them were validated by qRT-PCR. Most of their expressions changed during the pod development. Since some reports showed that Ca2+ signal transduction pathway is involved in hormone regulation pathway, these results implied that peanut seed development might be regulated by the collaboration of Ca2+ signal transduction pathway and hormone regulation pathway.
Highlights
Peanut (Arachis hypogaea L.) is an important crop member of the legume family and a major source of plant oil, proteins, essential vitamins and minerals that can be used for human consumption, animal feed, bioenergy, and health products (Higgs, 2002; Li et al, 2010, 2011)
Calcium is an essential macroelement for plant growth, and a second messenger involved in regulating diverse physiological processes (Poovaih and Ready, 1993)
Calcium deficiency in soil can results in a decrease in yield, e.g., unfilled pods (Cox et al, 1982)
Summary
Peanut (Arachis hypogaea L.) is an important crop member of the legume family and a major source of plant oil, proteins, essential vitamins and minerals that can be used for human consumption, animal feed, bioenergy, and health products (Higgs, 2002; Li et al, 2010, 2011). Several plant hormones have long been known to play a significant role in peanut gynophore elongation and embryo differentiation, such as auxin (Jacobs, 1951; Moctezuma and Feldman, 1996), the ration of NAA and kinetin (Ziv and Zamski, 1975), Transcriptome Analysis of Pod Development. Truncatula (MtCAMTAs) were responsive to the four hormones, including IAA, salicylic acid (SA), jasmonic acid (JA), and ABA, which play critical roles in the regulation of nodule organogenesis in legumes. It seems that the ripening of strawberry fruit are co-regulated by phytohormone and calcium signal transduction (Chen et al, 2016). There is a comprehensive understanding of calcium physiology related to peanut abiotic stress resistance, it is of vitally important to isolate and characterize more candidate genes for understanding some mechanisms regulating peanut pod development, especially Ca2+ and hormone regulating pathway
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