SIMILARITIES IN GENE-EXPRESSION DURING THE POSTHARVEST-INDUCED SENESCENCE OF SPEARS AND NATURAL FOLIAR SENESCENCE OF ASPARAGUS

Changes in gene expression and tissue composition were investigated du ring foliar development and natural senescence of asparagus (Asparagus officinalis L.). Three phases in development and senescence of the fo liage were characterized: early fern growth, mature fern, and senescen ce, when a marked loss of chlorophyll, sucrose, and protein occurred a nd major changes in translatable mRNAs were detected. Transcripts for three asparagus spear harvest-induced cDNA clones, pTIP9, pTIP11, and pTIP12 (G.A. King and K.M. Davies [1992] Plant Physiol 100: 1661-1669) , accumulated during natural foliar senescence, suggesting that the un derlying regulatory mechanisms may be similar in both developmental si tuations. We have used our knowledge of asparagus spear physiology, th e probable proteins encoded by the cDNA clones, and our fern developme nt data to propose that sugar depletion regulates the accumulation of at least pTIP12 transcripts in senescing asparagus tissue.