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ARS Home » Northeast Area » Kearneysville, West Virginia » Appalachian Fruit Research Laboratory » Innovative Fruit Production, Improvement, and Protection » Research » Publications at this Location » Publication #238748
Title: Stone formation in peach fruit exhibits spatial coordination of the lignin and flavonoid pathways and similarity to Arabidopsis dehiscence

Author
item Dardick, Christopher - Chris
item Callahan, Ann
item CHIOZZOTTO, R. - University Of Milan
item SCHAFFER, R. - Plant And Food Research
item PIAGNANI, M. C. - University Of Milan
item Scorza, Ralph

Submitted to: BioMed Central Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/9/2010
Publication Date: 2/12/2010
Citation: Dardick, C.D., Callahan, A.M., Chiozzotto, R., Schaffer, R., Piagnani, M., Scorza, R. 2010. Stone formation in peach fruit exhibits spatial coordination of the lignin and flavonoid pathways and similarity to Arabidopsis dehiscence. BioMed Central Biology. 8:13.

Interpretive Summary: Stone fruit, such as peach, plum, cherry, apricot, and almond, have a hard material surrounding the seed that is called stone. The stone is thought to have evolved to protect the seed from diseases and consumption. The stone tissue is composed of material very similar to wood but more densely packed resulting in a substance that is even harder than wood. One of the major components of stone, lignin, is made from a biochemical pathway that also is responsible for flavor components, color components, and anti-disease components of the fruit tissue. Understanding how these pathways interact to provide the necessary components will provide the information necessary to effectively obtain trees that produce fruit with higher degrees of flavor, color, disease resistance and even anti-oxidants for human health. Gene activity during the formation of the stone tissue and development of fruit flesh and skin was monitored in peach fruit for the first 60 days after bloom which is when the stone hardens. Many of the genes involved in the pathways for lignin, color development, and anti-disease components were expressed during this time. Subsets of these genes were specifically expressed in stone, skin, and/or flesh at different developmental times. This suggests that each tissue expresses only those genes necessary to produce each component, i.e. lignin only in the stone tissue and color only in the skin. By grouping the genes that are only expressed in one tissue, the elements that regulate that expression pattern can be identified. This knowledge will allow for the manipulation of specific components of each pathway without affecting other processes, i.e. increase anti-disease components without decreasing color.

Technical Abstract: Stone fruits, including peach (Prunus persica), plum (Prunus domestica, Prunus salicina), apricot (Prunus armeniaca), cherry (Prunus cerasus, Prunus avium), and almond (Prunus dulcis), have a hard shell or stone surrounding the seed. The stone is formed through lignification of the fruit endocarp, a process that occurs in a number of agriculturally important crop species called drupes. Little is known about the biochemical, genetic, and regulatory processes responsible for endocarp lignification. Here, we show that lignin deposition in peach initiates near the blossom end within the endocarp layer and proceeds in a distinct spatial-temporal pattern. Microarray studies of young fruit development identified a sharp and transient induction of numerous phenylpropanoid, lignin, and flavonoid pathway genes concurrent with stone hardening. Quantitative PCR (qPCR) studies revealed that some phenylpropanoid and lignin pathway genes were induced only in the endocarp over a 10-day-period, while two lignin genes appeared to be co-regulated with flavonoid pathway genes which showed a multi-phasic induction pattern over a 20-day-period. To spatially define the observed expression patterns, fruit were dissected into endocarp, mesocarp (flesh), and exocarp (skin). qPCR analysis showed that there are separate flavonoid pathway induction events in the endocarp, then mesocarp, and finally exocarp. Comparison to other fruit studies revealed that flavonoid pathway induction is conserved in apple, while lignin pathway induction is not. Collectively, the data reveals how the lignin and flavonoid pathways are temporally and spatially coordinated in developing peach fruit to presumably avoid competition for shared phenylpropanoid pathway derived precursors.