Abstract
Silk protein is synthesized in the silkgland of silkworm, Bombyx mori L. It is evident that silk productivity is one of the high heritable characters from the genetical aspects. It is also changed with the environmental circumstances. With this regard, this paper dealt with the varietal patterns of silkgland development and the factors concerning to the silk productivity of silkgland of silkworm by the synthesis of nucleic acids, profiles of amino acids and histological basis, using the eight parent silkworm varieties and their F$_1$ hybrids. 1. The weight of silkgland per larva increased proportionally in the F$_1$ hybrids which were crossed between longer silk yielding varieties. The silk content to the weight of the silkgland was higher in the longer silk yielding varieties than that in the shorter silk yielding varieties. 2. It was observed that the morphological changes of nuclei took place in the posterior silkgland cells with the larval development of the 5th instar. In varietal aspect, Jam 107 and Jam 108, longer silk yielding varieties, showed more branches in nuclei than the $N_2$ and $C_{60}$ which were shorter yielding ones. 3. It was observed that there was a high correlation between RNA content per unit weight of silkgland on the 6th day stage of 5th instar and silk productivity both in the parents and their F$_1$ hybrids. 4. RNA and DNA synthesis brought about thirty percent increase in the posterior silkgland of the longer silk yielding varieties during the 2nd day to the 4th day stages of the 5th instar, when compared with those in the posterior silkgland of the shorter silk yielding varieties. 5. RNA/DNA ratio in the posterior silkgland on the 2nd day and 4th day stages of the 5th instar was more increased in the longer silk yielding varieties than the shorter silk yielding varieties. 6. It was shown that DNA content for the longer silk yielding varieties came to be 374$\mu\textrm{g}$ per larva in the posterior division of silkgland on the 4th day stage of 5th instar, whereas it was 199$\mu\textrm{g}$ per larva for the shorter silk yielding varieties. 7 There was 34.8％ Alanine, 22.8％ Glycine, 9.1％ Serine and 7.3％ Tyrosine in the posterior division of silkgland as major amino acids. It is noticed that there was a little differences between the amino acids composition of posterior silkgland and silk fibroin. 8. There was some differences in the amino acids composition of posterior silkgland between pure lines and their hybrids. Glycine, Serine and acidic amino acids, essential to silk formation, seemed to be increased in the F$_1$ hybrids, whereas other amino acids such as Valine, Iso-leucine, Leucine, Lysine. Phenylalanine, Histidine and Arginine were reduced. 9. The content of Glycine, Alanine and Serine in the posterior division of silkgland was elevated in the longer silk yielding varieties than the others. Consequently. these three amino acids in the posterior silkgland seemed to be related to the silk yielding ability in the longer silk yielding varieties.s.
가잠의 견사물질 생성능력에 대한 견사선의 특이성을 구명코저 견사생산성이 다른 8개 원종과 그 F$_1$교잡종에 대하여 견사선의 성장 및 조직학적 특성, 후부견, 사선의 RNA 및 DNA합성과 그 아미노산조성 등을 조사한 결과 다음과 같을 결론을 얻었다. 1) 견사생성량이 다론 가잠품종간 F$_1$ 교배조를 만들 경우 다사량 품종은 5령유충기의 잠체중대 견사선중비 및 견사선중대 견사생성량비가 다사량 품종에 비하여 증가되었다. 2) 후부견사선의 조직학적 관찰에서 견사물질합성이 활발히 전개될 때는 세포핵의 크기 및 분지가 증대하고 5령 96시간째 세포핵의 형태에 있어서 견사생성량이 가장 적은 품종인 $N_2$ 및 $C_{60}$의 세포핵은 잠107, 잠108 등의 것에 비하여 크기가 작고 단순한 형태를 취하였다. 3) 가잠 후부견사선의 RNA함유율은 다사량계 품종이 소사량계 품종에 비하여 높았고 잠품종간 F$_1$ 교배조를 만들 경우 견사생성량과 RNA 함유율은 정상관으로 비례하였다. 4) 가잠 5령유충기중 5령 3일을 전후(2일~4일) 한 후부견사선의 RNA 및 DNA 생성량의 증가율은 다사량계품종이 소사량계에 비하여 약 30%정도 높았다. 5) 가잠 5령유충기(2~4일)의 후부견사선에 있어서 DNA에 의한 RNA 생성효율은 다사량계가 소사량 계품종에 비하여 높았다. 6) 다사량계 잠품종의 후부견사선 DNA 생성량은 5령 4일째 374$\mu\textrm{g}$/두인데 비하여 소사량계품종은 199$\mu\textrm{g}$로서 약 53%정도이었다. 7) 가잠 후부견사선의 아미노산 조성에 있어서 함유량이 가장 높은 것은 Alanine 34.8%이며 Glycine 22.8%, Serine 9.1%, Tyrosine 7.3%의 순으로서 견사 fibroin의 아미노산조성과는 달리 Glycine 함량이 Alanine에 비하여 적었다. 8) 가잠 원종과 교잡종의 후부견사선 아미노산 조성에 있어서 Valine, Isoleucine, Leucine, Phenylalanine, Lysine, Histidine 및 Arginine등 잠체성장에 대한 영양성 아미노산은 원종에 비교적 많이 함유되었고 Glycine Serine, Aspartic acid, Glutamic acid등 비영양성 아미노산과 Threonine은 F$_1$ 교잡종에 비교적 많이 함유되었다. 9) 견사 생성량이 다른 가잠 품종간의 F$_1$ 교배조에 있어서 후부견사선의 아미노산조성중 G.A.S.(Glycine+Alanine+Serine)함량은 다사량 품종일수록 증가되었다.